Preheat your oven to 400°F (200°C). Gather all ingredients and line a baking sheet with parchment paper.

Roll out the puff pastry sheets, cut them into 4x3 inch rectangles, and prick each rectangle with a fork.

Arrange the pastry rectangles on the baking sheet, cover with another parchment sheet, and place an additional tray on top.

Bake for 15-20 minutes until golden brown. Cool completely on a wire rack.

Heat the milk in a saucepan over medium-low heat until steamy, stirring occasionally.

In a bowl, whisk egg yolks, sugar, and cornstarch until smooth, then add the warm milk gradually while whisking.

Return the mixture to the saucepan, cook on medium-low for 5-7 minutes, stirring until thick.

Remove from heat and stir in butter and vanilla extract until combined.

On a serving dish, layer the pastry and custard, finishing with a layer of pastry on top.

Cover with plastic wrap and refrigerate for at least 4 hours or overnight.

Dust the top with powdered sugar and garnish with fresh berries before serving.