Preheat your oven to 400°F (200°C) . Line two baking sheets with parchment paper.
In a saucepan over medium heat, combine the water, butter, and salt. Bring to a boil, stirring until the butter melts completely.
Remove from heat and add the flour all at once. Stir vigorously with a wooden spoon until the mixture forms a smooth ball and pulls away from the sides of the pan.
Return the pan to low heat and cook for 1–2 minutes, stirring constantly, to dry out the dough slightly. Transfer to a mixing bowl and let it cool for 5 minutes.
Beat in the eggs one at a time, ensuring each egg is fully incorporated before adding the next. The dough should be smooth, shiny, and pipeable.
Step 2: Bake the Choux Layers
Transfer the dough to a piping bag fitted with a round tip. Pipe three 8-inch circles onto the prepared baking sheets (two for the layers and one for crumbs).
Bake for 25–30 minutes , or until the pastry is puffed, golden brown, and hollow-sounding when tapped. Let cool completely on a wire rack.
Step 3: Make the Pastry Cream
In a saucepan, heat the milk with the vanilla bean (split and scraped) over medium heat until just simmering. Remove from heat and let the vanilla infuse for 5–10 minutes.
In a mixing bowl, whisk together the egg yolks, sugar, and cornstarch until pale and thick. Gradually whisk in the warm milk.
Return the mixture to the saucepan and cook over medium heat, whisking constantly, until thickened (about 5–7 minutes). Remove from heat and stir in the butter and vanilla extract.
Transfer the pastry cream to a bowl, cover with plastic wrap (pressing it directly onto the surface to prevent a skin), and chill completely.
Step 4: Whip the Cream
In a mixing bowl, beat the heavy cream, powdered sugar, and vanilla extract until stiff peaks form.
Step 5: Assemble the Cake
Slice one of the choux pastry layers horizontally to create two thin layers. Reserve the second layer for the top and crumble the third for decoration.
Spread half of the pastry cream evenly over the bottom layer. Top with a layer of whipped cream. Repeat with the next layer of pastry, pastry cream, and whipped cream.
Place the final choux layer on top and frost the entire cake with the remaining whipped cream.
Sprinkle the crumbled choux pastry over the top and sides for texture. Garnish with powdered sugar, fresh berries, or chocolate shavings if desired.
