Making the Lemon Curd

1. Prepare Ingredients: In a medium-sized saucepan, combine the lemon juice, lemon zest, and granulated sugar.
2. Whisk Eggs: In a separate bowl, whisk the eggs until well combined.
3. Combine Mixtures: Gradually add the whisked eggs to the saucepan, whisking constantly to prevent curdling.
4. Cook Curd: Place the saucepan over medium heat, stirring continuously, until the mixture thickens and coats the back of a spoon (about 7-10 minutes).
5. Add Butter: Remove from heat and add the cubed butter, stirring until fully melted and incorporated.
6. Cool: Transfer the lemon curd to a bowl, cover with plastic wrap (pressing it onto the surface to prevent a skin from forming), and refrigerate until completely cool.

Preparing the Mascarpone Layer

1. Beat Cream and Sugar: In a large mixing bowl, combine the heavy cream and powdered sugar. Beat with an electric mixer until soft peaks form.
2. Add Mascarpone and Flavorings: Add the mascarpone cheese, lemon zest, lemon juice, and vanilla extract to the whipped cream. Beat until smooth and well combined.
3. Chill: Cover and refrigerate the mixture until ready to assemble the parfaits.

Making the Crumble Layer

1. Combine Ingredients: In a small bowl, mix the graham cracker crumbs, melted butter, and sugar until well combined.
2. Bake (Optional): For a crunchy texture, spread the mixture on a baking sheet and bake at 350°F (175°C) for 8-10 minutes. Allow to cool completely.

Assembling the Parfaits

1. Layer Crumble: In serving glasses or bowls, spoon a layer of the graham cracker crumble.
2. Add Lemon Mascarpone: Add a generous layer of the lemon mascarpone mixture on top of the crumble.
3. Layer Lemon Curd: Spoon a layer of lemon curd over the mascarpone layer.
4. Repeat: Repeat the layers until the glasses are filled, ending with a layer of lemon curd.
5. Chill: Refrigerate the assembled parfaits for at least 2 hours to allow the flavors to meld.

Garnishing

1. Add Berries: Top each parfait with fresh berries.
2. Decorate: Garnish with mint leaves and thin lemon slices for an elegant touch.