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 some at a time while whisking, making sure there are no lumps.

Place the pan over medium heat and stir continuously until it reaches a slow boil. The cream will thicken, so be careful not to let it stick to the bottom. Lower the flame and cook for a couple of more minutes, until you reach the desire thickness. Pour the cream in a glass bowl, cover with plastic wrap against the surface and let it cool down.

Preheat the oven to 400F. Roll out the puff pastry and cut into squares. I did 6 large squares (about 5 inches in side each), but you're welcome to cut as big or as small as you wish.

Using a pointy knife cut a half inch edge around the square (two L shapes) leaving two opposite corners uncut, as shown in my photos.

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 (1 tablespoon of milk mixed with one egg yolk). If you'd like sprinkle the edges with crystalized sparkling sugar.

Bake at 400F for about 15-18 minutes. Check the pastries after about 10 minutes. If the middle part is puffed up, prick again with a fork to deflate. Remove from the oven and let the pastries cool down.

Right before serving, whisk the custard until smooth. Pipe or spoon some cream in the middle of each pastries. Note: this recipe will give you plenty of custard to fill with a lot of cream.

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