Decadent Hazelnut Mocha Bars

There are some desserts that are merely good, and then there are those that create a core memory. These Decadent Hazelnut Mocha Bars fall firmly into the latter category. The first time I pulled a pan of these from the oven, my kitchen was instantly transformed into a high-end European café. The intoxicating aroma of rich, dark chocolate, freshly brewed espresso, and deeply toasted hazelnuts filled every corner of our home, drawing my family to the kitchen like a magnet. I remember the look on my husband’s face after his first bite—a moment of silent, wide-eyed bliss before he declared them “the best thing to ever come out of that oven.” They have since become my signature dessert, the go-to treat for everything from cozy winter evenings by the fire to celebratory potlucks where I want to bring something truly special. The magic of these bars lies in their incredible texture and flavor complexity. They start with a buttery, crisp hazelnut shortbread crust that provides the perfect foundational crunch. On top of that sits a layer of what can only be described as the fudgiest, most intensely chocolatey brownie-like filling you’ve ever experienced, supercharged with a bold mocha kick. The final flourish is a silky-smooth chocolate ganache topping, studded with more toasted hazelnuts for a delightful textural contrast. Every bite is a journey: first the snap of the ganache, then the melt-in-your-mouth fudgy center, and finally the crumbly, nutty crust. They are sophisticated yet comforting, impressive yet surprisingly straightforward to make. This recipe is more than just a set of instructions; it’s a guide to creating a truly unforgettable dessert experience that will have your friends and family begging for the recipe.

Ingredients

This recipe is broken down into three essential components: the crust, the filling, and the ganache topping. Using high-quality ingredients will significantly elevate the final flavor.

For the Hazelnut Shortbread Crust:

• 1 ½ cups all-purpose flour: The structural base for our buttery crust.
• ¾ cup raw hazelnuts, finely ground: Provides the signature nutty flavor and a delicate, sandy texture.
• ½ cup granulated sugar: Adds a touch of sweetness and helps the crust caramelize.
• ¼ teaspoon fine sea salt: Balances the sweetness and enhances the overall flavor.
• ¾ cup (1 ½ sticks) unsalted butter, cold and cubed: Creates the flaky, tender, shortbread-like texture. It must be cold to achieve the correct consistency.

For the Fudgy Mocha Filling:

• 1 cup (2 sticks) unsalted butter, cut into pieces: The key to a rich, moist, and fudgy center.
• 8 ounces high-quality bittersweet or dark chocolate (60-72% cacao), chopped: The heart of the recipe; using good quality chocolate is non-negotiable for a deep, complex flavor.
• 3 tablespoons instant espresso powder: Dissolves completely to infuse the filling with a robust coffee flavor that beautifully complements the chocolate.
• 1 ½ cups granulated sugar: Sweetens the filling and contributes to the dense, fudgy texture.
• 4 large eggs, at room temperature: Binds the filling together and adds richness. Room temperature eggs incorporate more easily.
• ½ cup chocolate-hazelnut spread (like Nutella): Adds another layer of hazelnut flavor and incredible creaminess.
• 1 teaspoon pure vanilla extract: Enhances and rounds out the chocolate and coffee notes.
• ½ cup all-purpose flour: Provides just enough structure to hold the bars together without making them cakey.
• ¼ teaspoon fine sea salt: A crucial ingredient to cut through the richness and make the chocolate flavor pop.

For the Silky Chocolate Ganache Topping:

• 6 ounces high-quality semi-sweet chocolate, finely chopped: Forms the base of the smooth, luxurious ganache layer.
• ⅔ cup heavy whipping cream: The liquid component that melts the chocolate and creates a silky, pourable consistency.
• ½ cup raw hazelnuts, toasted and roughly chopped: For sprinkling on top, adding a final layer of crunch and toasted nutty flavor.

Instructions

Follow these detailed steps carefully for perfect results. Patience, especially during the cooling stages, is key to achieving clean, beautiful bars.

Step 1: Prepare the Oven and Pan

Begin by preheating your oven to 350°F (175°C). Take a 9×13-inch baking pan and line it with parchment paper, leaving a 2-inch overhang on the two long sides. This parchment “sling” is essential for easily lifting the bars out of the pan for cutting later. Lightly grease the parchment paper and any exposed sides of the pan with butter or non-stick spray.

Step 2: Make the Hazelnut Shortbread Crust

In the bowl of a food processor, combine the 1 ½ cups of all-purpose flour, ¾ cup of finely ground hazelnuts, ½ cup of granulated sugar, and ¼ teaspoon of sea salt. Pulse a few times to evenly mix the dry ingredients. Add the cold, cubed ¾ cup of unsalted butter to the food processor. Pulse in short bursts, about 10-15 times, until the mixture resembles coarse, wet sand with some small, pea-sized butter pieces remaining. Be careful not to over-process; you don’t want it to form a solid ball of dough.

Step 3: Press and Bake the Crust

Transfer the crumbly mixture into your prepared 9×13-inch baking pan. Use your fingers or the flat bottom of a measuring cup to press the mixture firmly and evenly across the bottom of the pan, creating a solid, uniform layer. Bake in the preheated oven for 15-18 minutes, or until the edges are lightly golden brown and the crust looks set and dry. Once baked, remove the pan from the oven and set it on a wire rack to cool slightly while you prepare the filling. Do not turn off the oven.

Step 4: Prepare the Fudgy Mocha Filling

In a medium, heatproof bowl, combine the 1 cup of unsalted butter and the 8 ounces of chopped bittersweet chocolate. Create a double boiler by setting the bowl over a saucepan filled with about an inch of gently simmering water (ensure the bottom of the bowl does not touch the water). Stir the mixture occasionally with a silicone spatula until the butter and chocolate are completely melted, smooth, and glossy. Remove the bowl from the heat and immediately whisk in the 3 tablespoons of instant espresso powder until it is fully dissolved. Set the chocolate mixture aside to cool for about 5-10 minutes. It should be warm to the touch, not hot.

Step 5: Combine the Filling Ingredients

In a separate large mixing bowl, whisk together the 1 ½ cups of granulated sugar and the 4 room-temperature large eggs until the mixture is pale, slightly frothy, and well-combined, about 1-2 minutes. This incorporates a little air for a lighter fudginess. Whisk in the ½ cup of chocolate-hazelnut spread and the 1 teaspoon of vanilla extract until smooth.

Step 6: Finish the Batter

Gently pour the slightly cooled, melted chocolate-espresso mixture into the egg and sugar mixture. Whisk slowly until just combined. Be careful not to overmix at this stage. Finally, add the ½ cup of all-purpose flour and ¼ teaspoon of sea salt. Switch to a silicone spatula and fold the dry ingredients in until no streaks of flour remain. Again, do not overmix; stop as soon as everything is incorporated. Overmixing develops gluten and will result in a cakey, rather than fudgy, texture.

Step 7: Assemble and Bake the Bars

Pour the finished Fudgy Mocha Filling evenly over the pre-baked hazelnut crust in the pan. Use an offset spatula or the back of a spoon to spread the filling into a smooth, even layer, making sure it reaches all the corners. Place the pan back into the 350°F (175°C) oven and bake for 25-30 minutes. The bars are done when the edges are set and slightly puffed, and the center is mostly set but still has a very slight jiggle when the pan is gently shaken. A toothpick inserted into the center should come out with moist, fudgy crumbs attached, not wet batter. It’s better to slightly underbake than overbake to ensure maximum fudginess.

Step 8: Cool the Bars Completely

This is a critically important step. Remove the pan from the oven and place it on a wire cooling rack. Let the bars cool completely in the pan at room temperature, which will take at least 2 hours. For the best results and cleanest cuts, after they have cooled to room temperature, cover the pan with plastic wrap and transfer it to the refrigerator to chill for another 2-3 hours, or even overnight. Chilling solidifies the bars and makes the ganache application and cutting much easier.

Step 9: Make the Silky Chocolate Ganache

Once the bars are fully chilled, prepare the ganache. Place the 6 ounces of finely chopped semi-sweet chocolate in a medium heatproof bowl. In a small saucepan, heat the ⅔ cup of heavy whipping cream over medium heat until it just begins to simmer around the edges. Do not let it come to a rolling boil. Immediately pour the hot cream over the chopped chocolate. Let it sit, untouched, for 5 minutes. This allows the heat from the cream to gently melt the chocolate. After 5 minutes, whisk the mixture, starting from the center and working your way out, until the ganache is completely smooth, shiny, and emulsified.

Step 10: Top and Finish the Bars

Pour the warm ganache over the chilled bars in the pan. Use an offset spatula to spread it into a thin, even layer that covers the entire surface. Immediately sprinkle the ½ cup of toasted, chopped hazelnuts evenly over the ganache.

Step 11: Final Chill and Serve

Return the pan to the refrigerator for at least 30-60 minutes, or until the ganache is firm to the touch. Once the ganache is set, use the parchment paper overhangs to carefully lift the entire slab of bars out of the pan and onto a cutting board. For the cleanest cuts, use a large, sharp chef’s knife. Dip the knife in hot water and wipe it clean between each cut. Cut the slab into your desired size—24 small squares or 16 larger bars. The bars are best served at cool room temperature.

Nutrition Facts

• Servings: 24 bars
• Calories per serving: Approximately 350 kcal. A rich, decadent treat perfect for a special occasion.
• Fat: Approximately 22g. Primarily from the butter, hazelnuts, and chocolate, contributing to the rich flavor and melt-in-your-mouth texture.
• Carbohydrates: Approximately 35g. Provides the energy and structure of the bars, coming from the flour and sugars.
• Sugar: Approximately 25g. This is a dessert, after all! The sugar content is essential for the classic sweet, fudgy brownie-like quality.
• Protein: Approximately 4g. A small amount derived from the eggs, flour, and hazelnuts.

Preparation Time

This recipe requires some patience, particularly for the cooling stages, but the active time is quite manageable. Plan accordingly for the best results.

• Active Preparation Time: 30-40 minutes (includes making the crust, filling, and ganache).
• Baking Time: 40-48 minutes total (15-18 for the crust, 25-30 for the filling).
• Cooling & Chilling Time: Minimum 4 hours (essential for setting and cutting).
• Total Time: Approximately 5.5 hours.

How to Serve

These Hazelnut Mocha Bars are stunning on their own, but they can be elevated even further with the right pairing. Here are a few ideas for serving them:

• For the Ultimate Coffee Lover:
  • Pair a bar with a freshly brewed cup of dark roast coffee or a strong Americano. The bitterness of the coffee will cut through the richness of the bar beautifully.
  • Serve alongside a foamy cappuccino or latte for a luxurious coffee-house experience at home.
• For an Elegant Dinner Party Dessert:
  • Serve a single, perfectly cut bar on a small dessert plate.
  • Add a small scoop of high-quality vanilla bean or coffee-flavored ice cream on the side.
  • Garnish the plate with a dusting of cocoa powder, a single fresh raspberry for a pop of color, or a drizzle of caramel sauce.
• For a Casual, Cozy Treat:
  • Enjoy a bar with a tall glass of cold milk. The simple creaminess of the milk is a perfect counterpoint to the intense chocolate.
  • Warm the bar in the microwave for just 10-15 seconds to get the center slightly gooey and serve it in a bowl.

Additional Tips

Follow these eight tips to ensure your Decadent Hazelnut Mocha Bars are flawless every single time.

1. Toast Your Hazelnuts Properly. While the recipe calls for ground raw hazelnuts in the crust, toasting the ones for the topping is crucial. Spread them on a baking sheet and bake at 350°F (175°C) for 8-10 minutes, until fragrant and lightly browned. This deepens their flavor immeasurably and makes them crunchier.
2. Don’t Overbake the Filling. The key to a fudgy bar is a slightly underbaked center. The visual cue is a set edge and a center that has a slight jiggle. The residual heat will continue to cook the bars as they cool. Overbaking will lead to a dry, cake-like texture.
3. Embrace the Cooling Time. Do not rush the cooling and chilling process. It is the most important step for the texture and structure of the bars. Attempting to cut them while warm will result in a gooey mess. Chilling solidifies the butter and chocolate, ensuring you get those beautiful, clean-edged squares.
4. Ingredient Quality Matters. With simple, bold flavors like chocolate and coffee, the quality of your ingredients shines through. Use a high-quality dark chocolate (60% cacao or higher) you would enjoy eating on its own, and a good brand of instant espresso powder for the best, most authentic flavor.
5. Achieve Perfectly Clean Cuts. The secret to professional-looking bars is a hot, clean knife. Fill a tall glass with hot water. Dip your sharp chef’s knife into the water, wipe it dry with a paper towel, make one cut, and repeat the process. It’s tedious, but the results are worth it.
6. Room Temperature Eggs are a Must. Using room temperature eggs allows them to mix more evenly with the sugar and incorporate more air. This creates a more uniform and slightly lighter fudgy texture. To quickly bring eggs to room temperature, place them in a bowl of warm (not hot) water for 5-10 minutes.
7. Customize the Coffee Intensity. If you are a true coffee fanatic, you can increase the espresso powder to 4 tablespoons for an even bolder mocha punch. Conversely, if you prefer a more subtle coffee note, you can reduce it to 2 tablespoons.
8. Make-Ahead and Storage. These bars are an excellent make-ahead dessert. They can be stored in an airtight container in the refrigerator for up to a week. Their flavor actually deepens and improves after a day or two. For serving, let them sit at room temperature for 15-20 minutes to take the chill off.

Frequently Asked Questions (FAQ)

Q1: Can I make these bars gluten-free?
A: Yes, you can adapt this recipe to be gluten-free. For the crust and filling, substitute the all-purpose flour with a high-quality 1-to-1 gluten-free baking flour blend (one that contains xanthan gum). The texture will be very similar and just as delicious.

Q2: Can I use instant coffee instead of instant espresso powder?
A: While you can, it’s not recommended for the best flavor. Instant espresso powder has a much deeper, richer, and less acidic flavor that is specifically designed to complement chocolate. Instant coffee can sometimes taste a bit harsh or bitter in baked goods. If you must use it, use the same amount, but look for a dark roast variety.

Q3: Can I freeze these Hazelnut Mocha Bars?
A: Absolutely! These bars freeze beautifully. Once they are fully set and cut, arrange them in a single layer in a freezer-safe airtight container. Place a sheet of parchment or wax paper between layers to prevent them from sticking. They can be frozen for up to 3 months. To serve, thaw them in the refrigerator overnight.

Q4: My chocolate seized when I was melting it. What did I do wrong?
A: Chocolate “seizes” (becomes a thick, grainy paste) when it comes into contact with even a tiny drop of water. This is why using a double boiler is recommended. Ensure the bottom of your bowl doesn’t touch the simmering water, and be careful that no steam or water gets into the chocolate. If it does seize, you can sometimes save it by vigorously whisking in a tablespoon of boiling water or neutral oil, but the texture may be slightly altered.

Q5: Can I use a different type of nut?
A: Yes, you can. While hazelnuts are classic for a mocha pairing, these bars would also be fantastic with almonds or pecans. Simply substitute the hazelnuts with an equal amount of finely ground almonds or pecans in the crust and use chopped toasted almonds or pecans for the topping.

Q6: I don’t have a 9×13-inch pan. Can I use a different size?
A: You can, but you will need to adjust the baking time. An 8×8-inch or 9×9-inch square pan will work, but the bars will be much thicker. You will need to increase the baking time for the filling, likely by 10-15 minutes. Start checking for doneness at the 30-minute mark and bake until a toothpick comes out with moist crumbs.

Q7: My shortbread crust seems too crumbly. How can I fix this?
A: The crust mixture is supposed to be crumbly, like wet sand. The key is to press it very firmly and evenly into the pan. This pressure is what helps it bind together during baking. If it still feels exceptionally dry, it might be due to a slight mismeasurement of flour. You can add a teaspoon of cold water to the mixture in the food processor and pulse once or twice to help it come together.

Q8: What is the best type of chocolate to use for this recipe?
A: For the filling, a high-quality bittersweet or dark chocolate with a cacao percentage between 60% and 72% is ideal. This provides a deep, rich chocolate flavor that isn’t overly sweet and balances the sugar in the recipe. For the ganache, a semi-sweet chocolate (around 50-60% cacao) works well as it creates a silkier, slightly sweeter topping that contrasts nicely with the darker filling. Avoid using milk chocolate, as it will make the bars too sweet.

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