Put softened butter, water and salt in a thick-bottomed saucepan and bring to a brief boil, stirring constantly so that the butter melts before it boils.
Take the saucepan off the heat, immediately add flour in one swoop and mix briskly with a wooden wooden spoon until a large ball of dough has formed.
Put the saucepan back on the stove and heat the dough, stirring and turning it with a wooden spoon, for about 1 - 2 minutes, until the dough comes off the bottom of the saucepan as a dumpling, leaving a white layer of starch.
Take the saucepan off the heat, transfer the dough to a clean mixing bowl and let it cool to lukewarm.
Using a wooden spoon or a mixer, gradually stir into the dough, one at a time, as many eggs as it takes to make it shiny and stick to a wooden spoon in peaks. It is best to whisk the last egg in a small bowl and add just enough of it to the dough in batches until it has the right consistency. The dough must be spreadable, in no case runny or solid.
Fill the dough into a piping bag with a round hole nozzle or a star nozzle and pipe on a baking tray lined with baking paper about 10 cm long strips with plenty of space between them.
Bake the pastries in a preheated oven at 190 °C top and bottom heat for about 35 minutes until golden brown and let them cool down.