Set the oven to 400°F (200°C) and prepare a baking tray with a sheet of parchment paper.
In a medium saucepan, combine the water, butter, and salt, and bring to a rolling boil over medium heat.
Immediately add the flour in one motion and stir rapidly until the mixture clings together and detaches cleanly from the sides of the pot.
Remove from the burner and allow the dough to cool for 5 minutes.