Step 1: Prepare the Pastry

1. Preheat your oven to 400°F (200°C) and line two baking sheets with parchment paper.
2. Lightly dust your work surface with flour and roll out each puff pastry sheet to about 1/8-inch thickness.
3. Using a 2.5-inch round cookie cutter, cut out circles from the pastry. You should get approximately 12 circles from each sheet.
4. Place the pastry circles on the prepared baking sheets, leaving about 1 inch between each.
5. Brush each circle lightly with beaten egg and sprinkle with a little granulated sugar.
6. Place another piece of parchment paper on top of the pastry circles and then place another baking sheet on top to prevent excessive rising.
7. Bake for 12-15 minutes until golden brown and crisp.
8. Remove the top baking sheet and parchment paper for the last 2 minutes of baking to ensure the tops get golden.
9. Allow to cool completely on a wire rack.

Step 2: Make the Raspberry Filling

1. In a medium saucepan, combine the raspberries, sugar, and lemon juice.
2. Cook over medium heat until the raspberries break down and release their juices, about 5-7 minutes.
3. In a small bowl, mix cornstarch and water to create a slurry.
4. Slowly pour the cornstarch mixture into the simmering raspberry mixture, stirring constantly.
5. Continue cooking for another 2-3 minutes until the mixture thickens.
6. Remove from heat and stir in vanilla extract.
7. Transfer to a bowl and let cool completely. The filling will continue to thicken as it cools.
8. Once cooled, refrigerate for at least 30 minutes before using.

Step 3: Prepare the Vanilla Cream

1. In a large bowl, combine heavy whipping cream, confectioners’ sugar, and vanilla extract.
2. Beat using an electric mixer on medium-high speed until soft peaks form.
3. If using, fold in the mascarpone cheese gently until just combined.
4. Refrigerate until ready to assemble.

Step 4: Sort and Prepare Pastry Circles

1. Sort your baked pastry circles into pairs of similar size.
2. If any circles have puffed up too much, gently press down the centers to create a flatter surface.
3. Arrange half of the circles on your work surface or serving platter, flat side up.

Step 5: Assemble the Base Layer

1. Transfer the vanilla cream to a piping bag fitted with a small round tip.
2. Pipe a ring of vanilla cream around the edge of each pastry circle, creating a dam for the raspberry filling.
3. Spoon about 1 teaspoon of raspberry filling into the center of each cream ring.
4. Make sure the filling is level and doesn’t rise above the cream dam.

Step 6: Complete the Assembly

1. Top each prepared base with a matching pastry circle, pressing gently to secure.
2. Make sure not to press too hard or the filling will squeeze out.
3. Arrange the completed cookies on a serving platter.

Step 7: Finish and Garnish

1. Dust the tops of the cookies with confectioners’ sugar just before serving.
2. Optional: Add a small fresh raspberry on top of each cookie for an elegant presentation.
3. For an extra touch, drizzle with a little white chocolate if desired.