Preheat your oven to 400°F (200°C).

In a saucepan, combine 1 cup of water and ½ cup of unsalted butter over medium heat. Bring to a boil, then promptly add 1 cup of all-purpose flour and a pinch of salt, stirring until a dough forms.

Once the dough has cooled for about 5 minutes, add 4 large eggs one at a time, mixing thoroughly each time.

Divide the dough evenly into two portions and spread each portion onto the prepared baking sheets into rectangles about ¼ inch thick.

Bake for 30-35 minutes until golden brown. Allow to cool completely on wire racks.

In a medium saucepan, whisk together ½ cup of granulated sugar and ½ cup of cornstarch. Gradually whisk in 2 cups of milk and 4 egg yolks until well combined, cook over medium heat until thickened.

Remove custard from heat, stir in 1 teaspoon of vanilla extract and ½ cup of unsalted butter until melted. Cool to room temperature.

In a separate bowl, whip 1 cup of heavy cream until soft peaks form. Gently fold into the cooled custard mixture.

Take one cooled layer of pastry and spread the custard cream on top, then place the second pastry layer on top. Dust with powdered sugar before serving.