Preheat the oven to 400°F and line a baking sheet with parchment paper.

Roll out the puff pastry and cut into heart shapes using a cookie cutter or a knife. Place on the baking sheet.

Brush the tops with the egg yolk for a golden finish. Bake for 15 to 20 minutes, or until puffed and golden brown. Allow to cool completely.

While the pastry bakes, prepare the custard. In a saucepan no heat, combine your egg yolk and sugar. With a spatula, combine until the sugar and egg yolk are pale yellow.

Pour in your milk and combine with a spatula. Mix in your cornstarch and vanilla. Combine until no clumps.

Cook over medium heat, stirring constantly until thickened. If your egg starts to curdle, take off the heat immediately. As soon as clumps start to form, remove from heat and let cool. Keep stirring until thickened.

In a chilled bowl, whip the heavy cream until peaks form. Gently fold into the cooled custard to create a light cream filling.

Slice each pastry in half. Spoon or pipe the cream filling inside, then layer with fresh strawberries. Place the top half back on and dust with powdered sugar before serving.