Warm up the milk until hot (not boiling).

In a medium sized pan, whisk the egg yolks with the sugar and corn starch until light and fluffy. Add the milk gradually while whisking to avoid lumps.

Place the pan over medium heat and stir continuously until it reaches a slow boil. Cook until the cream thickens, about a couple of minutes. Add the vanilla extract and whisk. Pour the cream into a glass bowl, cover with plastic wrap, and let it cool down.

Preheat the oven to 400°F. Roll out the puff pastry and cut into squares (about 5 inches each).

Using a pointy knife, cut a half inch edge around the square, leaving two opposite corners uncut.

Fold the two cut corners up and over to the other side.

Prick the middle part with a fork. Brush the edges with milk or egg wash (a tablespoon of milk mixed with one egg yolk).

Bake at 400°F for about 15-18 minutes. Check after about 10 minutes; if the middle puffs up, prick it again with a fork to deflate. Remove from the oven and let cool.

Right before serving, whisk the custard until smooth. Pipe or spoon cream into the middle of each pastry.

Top with berries and almond slices. Sprinkle with powdered sugar if desired and serve.