Combine water, milk, butter, and salt in a medium saucepan and heat until it reaches a rolling boil. prep

Remove from heat and stir in the flour using a wooden spoon until a smooth dough forms. Continue stirring over low heat until the dough pulls away from the pan, about 2 minutes. mix

Transfer the dough to a mixing bowl and let it cool for 1 minute to prevent eggs from scrambling. prep

Add eggs one at a time, fully incorporating each before adding the next. Stir in Gruyère, black pepper, and nutmeg until evenly combined. mix

Fit a pastry bag with a ½-inch round tip and fill it with the dough. Pipe tablespoon-sized mounds onto prepared baking sheets, spacing them 2 inches apart. assemble

Sprinkle extra Gruyère on top if desired and bake in a preheated 400°F oven for 22 minutes, or until puffed and golden brown. bake

Serve immediately, or let cool and store in the refrigerator or freezer. Reheat in a 350°F oven until warm before serving. finish