1/2 cup milk
4 tablespoons butter
1/4 teaspoon kosher salt
pinch cayenne pepper
1 cup flour
4 large eggs
2 ounces grated Parmesan (1/2 cup)
6 ounces grated Gruyère (1 1/2 cups)
1/2 teaspoon black pepper
1 large egg yolk
sea salt, optional
Preheat the oven to 400º F.
In a heavy-bottomed saucepan, combine 1/2 cup of water, the milk, butter, kosher salt, and cayenne. Bring to a boil over medium-high heat, stirring occasionally. Immediately add the flour. Stir quickly into the mixture with a wooden spoon until the dough pulls away from the pan and forms a ball, cooking for an additional minute while stirring.
Remove the dough from the heat and place in a food processor, pulsing twice, and then allowing to cool at least five minutes. Mix in the eggs one at a time, pulsing after each addition until incorporated. Add in the cheese, reserving two tablespoons, and pepper and mix just until combined.
Place the dough in a pastry bag and pipe into 1-tablespoon rounds on a parchment- or baking-mat-lined baking sheet, 2″ apart. Alternatively, scoop balls using a small scoop or two spoons onto the lined baking sheet.
Beat the egg yolk with one teaspoon of water. Brush lightly over the top of the rounds with a pastry brush. Sprinkle with reserved cheese and a bit of sea salt, if desired.
Bake for 25 minutes, until rounds are golden brown and dry in the center. They should sound hollow when tapped.
Serve warm. These can be reheated for a few minutes in the oven just before serving.
Makes 32 bite-sized gougères