Turn the oven to 200 degrees celcius.
Bring water and butter to a boil in a saucepan.
When the liquid boils, add all the flour at once. Stir vigorously with a spoon. Stir over low heat until the dough gathers, becomes glossy, and releases the bowl. Then it needs to get off the heat right away.
Allow the dough to cool slightly. Meanwhile, whisk the eggs together in a bowl.
Put the dough in a mixer with a whisk or use an electric hand mixer. Add the equivalent of 1 egg at a time, whisking the dough well after each egg. In the end, the mixture should be quite sticky but still smooth and even.
Place 12 choux buns on a baking sheet lined with baking paper. This is most easily done with two spoons. It does not have to be that nice, as long as they are roughly the same size. You can also put the dough in a piping bag and pipe your choux buns on the baking tray.
Bake the choux buns for 30-35 minutes in the middle of the oven. Avoid opening the oven for the first 30 minutes. When the time is up and they are well golden, take one of the buns out and see if it collapses. If it collapses, the baking time must be extended. If it does not collapse, you can take the rest out of the oven.
Place them on a rack so they can cool while you prepare the filling.