Preheat your oven to 400°F (200°C) and prepare a baking pan by greasing it or lining it with parchment paper.

In a medium saucepan, combine 1 cup of water and ½ cup of butter. Heat over medium until boiling, then remove from heat and stir in 1 cup of all-purpose flour to form a cohesive dough.

After the dough has cooled for about 5 minutes, add 4 large room-temperature eggs one at a time, stirring vigorously after each until glossy and smooth.

Spread the dough into your prepared baking pan and bake for 30–35 minutes, until golden brown and firm. Do not open the oven during baking.

Whisk together 2 cups of milk, ½ cup of sugar, and ¼ cup of cornstarch in a medium pot. Heat over medium-low, stirring until thickened, about 5–7 minutes. Stir in 1 tablespoon of vanilla extract off heat.

Let the baked pastry cool completely in the pan on a wire rack.

Once cool, slice the pastry in half horizontally. Spread custard over the bottom layer and top with the second half.

Chill the assembled cake in the refrigerator for at least 2 hours before serving.

Dust the top with powdered sugar before serving and enjoy the delightful textures.