Preheat your oven to 400°F (200°C). Roll out the puff pastry sheets and place them on a parchment-lined baking tray.

Score the edges with a knife to create a border, then prick the center with a fork to prevent puffing too much. Bake the pastry for about 15-20 minutes, or until golden brown.

In a saucepan over medium heat, combine the milk, half of the sugar, and vanilla.

In a separate bowl, whisk the egg yolks, cornstarch, and remaining sugar until smooth.

Once the milk mixture is steaming, slowly pour it over the egg mixture while whisking. Return the combined mixture to the saucepan and cook over low heat until thickened, stirring constantly.

Once the pastry cream has thickened, remove it from the heat and whisk in the unsalted butter.

Transfer the cream to a bowl, cover with plastic wrap directly on the surface to prevent a skin, and refrigerate until chilled.

Once the pastry is cool, slice each sheet in half horizontally, creating four equal layers.

Place one layer on a serving platter and spread a generous layer of pastry cream on top. Repeat with the next layer, and then top with the last layer.

To finish, dust the top layer with powdered sugar. For an added touch, melt some chocolate and drizzle it across the top for decoration.