Add water, milk and butter to a sauce pan, bring to a boil
Take the pan off the stove
Add flour and salt to the mixture and whisk well
Put pan back on the stove while whisking
It should become a dry-ish ball that won't stick to the pan
Add the eggs one by one and keep whisking, make sure the mixture doesn't split
Make little balls from the dough and put on a baking tray (lined with parchment paper)
Put tray in oven for 15-20 minutes on 200 degrees Celcius
Let cool down and then you can add any filling you like (jam, cream...)