1. Heat the oven to 425°F and line 2 baking sheets with parchment. Combine 1 cup water, the butter, and the salt in a 3-quart (or larger) saucepan; turn the heat to medium-high and bring to a boil. Cook, stirring, until the butter melts, just a minute or two.
2. Lower the heat to medium-low and add the flour all at once, stirring constantly. Keep cooking and stirring, scraping the bottom of the pot to prevent too much of the mixture sticking to the bottom, until the dough gets stiff, about 3 minutes. It’s okay if it’s crumbly and doesn’t form a ball.
3. Transfer the dough to a large mixing bowl or the work bowl of a stand mixer fitted with the paddle. (A hand mixer won’t cut it, but you can work relatively easily by hand with a sturdy soft spatula or wooden spoon.) Add the eggs one at a time, letting the machine run (or stirring hard by hand) after each addition. When the dough is ready, it will be a little shiny and crumbly but hold together when pressed. Fold in the cheeses until they’re distributed evenly.
4. Drop heaping teaspoonfuls onto the baking sheets and bake until puffed and lightly browned, 10 to 15 minutes. Immediately transfer to a wire rack to cool. Serve warm or at room temperature.

—Recipe developed by The Bittman Project for Bob’s Red Mill