Start by making the pastry cream because it needs cooling time. You can bake the puff pastry while the cream cools. If short on time, make pastry cream the day before.

Warm the milk: heat milk with half the sugar and lemon zest (if using) in a medium saucepan over medium heat until it’s steaming but not boiling.

Whisk the yolks: in a bowl, whisk egg yolks with the remaining sugar until pale. Add cornstarch and whisk until smooth.

Temper: slowly pour about 1/3 of the hot milk into the yolk mixture, whisking constantly to avoid scrambling.

Cook: pour the tempered mixture back into the saucepan with the remaining milk. Cook over medium heat, whisking constantly, until it thickens and comes to a gentle boil—about 1–2 minutes after it starts to bubble.

Finish: remove from heat, whisk in butter and vanilla. For extra smoothness, pass through a fine-mesh sieve into a bowl. Press plastic wrap directly onto the surface to prevent a skin and chill until cool (about 1–2 hours).

Preheat oven to 400°F (200°C).

On a lightly floured surface or parchment, unroll a sheet of puff pastry and gently smooth with a rolling pin to even thickness (don’t over-handle).

Transfer to a baking sheet lined with parchment. Prick the surface lightly with a fork all over to keep dramatic puffing to a minimum.

Brush with egg wash and sprinkle with a thin layer of sugar.

Top with another sheet of parchment and another baking sheet (or use baking weights) to keep it flat.

Bake 12–15 minutes until golden and crisp. Repeat with the second sheet. Let cool completely on a rack. Once cool, trim edges for clean layers—aim for three even rectangles per sheet (or as your serving plan dictates).

Beat cold heavy cream, powdered sugar, and vanilla to soft peaks. Fold the whipped cream gently into half of the cooled pastry cream if you want lighter, airier layers, or keep the creams separate for different textures.

Place a pastry layer on your serving platter.

Spread a generous, even layer of pastry cream (or cream-mascarpone mix).

Scatter fresh raspberries evenly—whole or halved depending on size.

Repeat: pastry, cream, raspberries for 3 stacked layers. Finish with a top pastry sheet.

Lightly dust with powdered sugar or pipe a thin line of whipped cream and decorate with raspberries and lemon zest.

Chill for at least 1 hour to let the layers settle and slice cleaner.

Use a sharp serrated knife and wipe between slices for neat pieces. Serve chilled or at cool room temperature.