Recipe for 50 small ones :
1 - Bring the water, butter and salt to boil in a saucepan. When boiling, pour the flour in one go and stir with a spatula leaving on low heat until you obtain a dough ball.
2 - Remove from the heat. Add the eggs one at a time, then the gruyere.
3 - Preheat the oven to 220° (Thermostat 7). Place small teaspoon size knobs of the dough on a baking tray.
4 - Bake for 15 minutes at 220° (Thermostat 7) then 15 minutes at 200° (Thermostat 6)