Weigh and measure all the ingredients.
Bring the water to a boil, add the butter, and let it melt in the hot water.
Add the flour all at once, stirring constantly.
Keep stirring over medium heat until the mixture forms a ball.
Dry out the dough over the heat for about 2 minutes, then transfer it to the bowl of a stand mixer.

Add the eggs one at a time, mixing with the whisk attachment. Wait until each egg is fully incorporated before adding the next.

Transfer the dough to a piping bag. Pipe large and small rounds for the choux, and bake for about 20 minutes at 400°F (200°C). For the small choux, 15 minutes is enough. Cool on a wire rack.

To make the pastry cream:

Place the egg yolks and sugar in a mixing bowl and whisk vigorously until pale.
Heat the milk with the vanilla bean and remove from heat once it boils.
Add the flour to the eggs, then pour in the hot milk.
Return the mixture to the saucepan and cook over heat, stirring constantly, until it thickens.
Let cool before using.