Let’s break down how to make these delightful Brownie Bottom Mini Cheesecakes step-by-step. Don’t worry, it’s easier than you might think!

Step 1: Prepare the Brownie Batter

1. Preheat your oven to 350°F (175°C). It’s crucial to preheat the oven to the correct temperature to ensure even baking and prevent the brownies and cheesecakes from being undercooked or overcooked.
2. Grease a muffin tin. You will need a standard 12-cup muffin tin. Generously grease each cup with cooking spray or butter. This will prevent the mini cheesecakes from sticking and make them easy to remove after baking. You can also use muffin liners, but for brownie bottoms, greasing the tin directly often works better to get a nice edge.
3. Combine dry ingredients. In a medium-sized mixing bowl, whisk together the all-purpose flour, unsweetened cocoa powder, granulated sugar, brown sugar, salt, and baking powder. Whisking ensures that the dry ingredients are evenly distributed and any lumps are broken up, leading to a smoother brownie batter.
4. Melt the butter. In a microwave-safe bowl or a saucepan over low heat, melt the unsalted butter completely. Melted butter is key to achieving a fudgy brownie texture. If using the microwave, melt in 30-second intervals, stirring in between, to prevent overheating. If using a saucepan, melt over low heat and remove from heat as soon as it’s melted.
5. Combine wet and dry ingredients. Pour the melted butter into the bowl with the dry ingredients. Stir with a spatula or wooden spoon until just combined. Be careful not to overmix at this stage. Overmixing can develop the gluten in the flour, leading to tougher brownies.
6. Add eggs and vanilla extract. Crack the eggs into the batter one at a time, mixing well after each addition. Then, stir in the vanilla extract. Mixing well after each egg ensures they are fully incorporated and contributes to the overall texture of the brownies.
7. Fold in chocolate chips (optional). If you desire extra chocolate chips in your brownie base, gently fold them into the batter now. Folding is a gentle mixing technique that prevents overmixing and keeps the chocolate chips evenly distributed.

Step 2: Assemble the Brownie Bottoms

1. Fill muffin cups with brownie batter. Spoon approximately 1-2 tablespoons of brownie batter into each greased muffin cup. You want to fill them about one-third to halfway full. This will leave enough room for the cheesecake filling on top.
2. Bake the brownie bottoms. Place the muffin tin in the preheated oven and bake for 10-12 minutes. The brownies are ready when a toothpick inserted into the center comes out with moist crumbs attached. They should be slightly set around the edges but still soft in the center. Don’t overbake at this stage, as they will continue to bake with the cheesecake filling.
3. Cool slightly. Remove the muffin tin from the oven and let the brownie bottoms cool in the tin for about 5-10 minutes while you prepare the cheesecake filling. This slight cooling period allows the brownie bottoms to set up a bit, making it easier to add the cheesecake filling.

Step 3: Prepare the Cheesecake Filling

1. Soften the cream cheese. Ensure your cream cheese is softened to room temperature. This is crucial for a smooth, lump-free cheesecake filling. If you’re short on time, you can microwave it in 15-second intervals, being careful not to melt it.
2. Beat cream cheese and sugar. In a large mixing bowl, beat the softened cream cheese and granulated sugar together with an electric mixer until smooth and creamy. Beat on medium speed until the mixture is light and fluffy. This step incorporates air into the filling, making it light and airy.
3. Add eggs one at a time. Beat in the eggs one at a time, mixing well after each addition, just until combined. Be careful not to overmix the batter at this stage, as overmixing can incorporate too much air and cause the cheesecakes to crack during baking.
4. Stir in vanilla extract, sour cream (optional), and lemon juice (optional). Stir in the vanilla extract, sour cream (if using), and lemon juice (if using). Mix until just combined. These ingredients add flavor and texture to the cheesecake filling.

Step 4: Assemble and Bake the Mini Cheesecakes

1. Pour cheesecake filling over brownie bottoms. Spoon the cheesecake filling evenly over the slightly cooled brownie bottoms in the muffin tin. Fill each muffin cup almost to the top, leaving a little space for expansion during baking.
2. Bake the mini cheesecakes. Return the muffin tin to the oven and bake for another 20-25 minutes. The cheesecakes are done when the edges are set, and the centers are just slightly jiggly. They should not be overly browned.
3. Cool in the oven (optional). For best results and to prevent cracking, turn off the oven and leave the oven door slightly ajar. Let the mini cheesecakes cool in the oven for about 30 minutes. This gradual cooling process helps prevent drastic temperature changes that can cause cracking.
4. Cool completely and chill. Remove the muffin tin from the oven and let the mini cheesecakes cool completely at room temperature. Once cooled, cover the muffin tin with plastic wrap and refrigerate for at least 2-3 hours, or preferably overnight. Chilling firms up the cheesecakes and enhances their flavor and texture.

Step 5: Serve and Enjoy!

1. Remove from muffin tin. Once chilled, gently remove the mini cheesecakes from the muffin tin. You can use a thin knife or spatula to loosen the edges if needed.
2. Garnish (optional). Garnish with your favorite toppings before serving, such as chocolate sauce, caramel sauce, fresh berries, whipped cream, or a dusting of cocoa powder.