Preheat your oven to 375°F (190°C). Roll out thawed puff pastry on a floured surface and cut into 6 equal squares, scoring a smaller square inside each piece.

Brush the scored pastry squares with beaten egg and sprinkle with granulated sugar. Bake for 15-18 minutes until puffed and golden, then cool completely.

Heat whole milk in a saucepan until steaming. In another bowl, whisk egg yolks, granulated sugar, cornstarch, and salt. Gradually whisk hot milk into egg mixture, then return to saucepan and cook until thickened, about 5-7 minutes.

Stir in pure vanilla extract, cover the custard with plastic wrap, and chill in the refrigerator for at least 30 minutes.

Once cooled, fill each pastry shell with custard, then top with fresh berries.

Dust with powdered sugar and garnish with fresh mint before serving.