Gougères

Lightly grease 2 baking sheets and preheat the oven to 425°F.

Combine 1 cup water, the butter, and the salt in a medium saucepan; turn the heat to medium-high and bring to a boil. Cook, stirring, until the butter melts, just a minute or two longer. Add the flour all at once and cook, stirring constantly, until the dough holds together in a ball, 5 minutes or less. The dough will get stiffer as you stir it; keep at it until the dough is smooth. Transfer the batter to a large mixing bowl or the work bowl of a stand mixer.

Add the eggs one at a time, beating hard after each addition (this is a little bit of work; use a stand mixer if you have one; a hand mixer will likely not be powerful enough). Stop beating when the mixture is glossy. Stir in the cheeses.