Preheat your oven to 400°F (200°C). Line baking sheets with parchment paper.

In a medium saucepan, combine 1 cup of water and 1/2 cup of unsalted butter. Bring to a boil over medium heat.

Remove from heat. Stir in 1 cup of all-purpose flour and a pinch of salt until a smooth dough forms.

Let the dough cool in the saucepan for about 5 minutes.

Add 4 beaten eggs to the dough one at a time, mixing thoroughly.

Divide the dough into two portions and spread onto baking sheets.

Bake for 30-35 minutes until golden brown. Cool completely.

In a saucepan, whisk together 1 cup of sugar and 1/4 cup of cornstarch. Gradually add 2 cups of milk while stirring. Cook until thickened.

Remove from heat and stir in 4 egg yolks and 1 teaspoon of vanilla extract.

Whip 1 cup of heavy cream until soft peaks form and fold into the custard mixture.

Assemble the cake by layering one pastry with custard and topping with the second pastry.

Dust with powdered sugar and chill for 30 minutes before serving.