8 tablespoons (1 stick) unsalted butter
1/4 teaspoon salt
1 cup flour
4 eggs, beaten
1 cup finely grated Gruyere cheese, divided
2 teaspoons Dijon mustard or 1 teaspoon dry mustard
1/2 teaspoon freshly ground pepper
Preheat oven to 400 F. Line baking sheets with parchment paper.
Combine the butter, salt and 1 cup water in a medium saucepan over low heat, stirring until butter has melted. Bring mixture to a boil, then remove pan from heat. Add the flour all at once and beat vigorously with a wooden spoon until dough comes together in a mass. Return pan to stove and, over medium heat, continue to beat dough for another minute until a thin film appears on bottom of pan.
Scrape dough into bowl of a stand mixer and beat on medium speed for 1 minute to cool it a bit. Before adding the beaten eggs, reserve about 1 tablespoon egg for glaze. Add eggs in 4 increments, letting each addition absorb completely into dough before adding next. Mixture may look sloppy but will magically come together in a very thick batter. (If you feel in need of a workout, beat eggs in by hand.)
Add 3/4 cup of the cheese, reserving rest for garnish. Beat in cheese with the mustard and pepper until well-blended.
Drop by tablespoonfuls, about 1 inch apart, onto parchment-lined baking sheets or use a pastry bag to pipe 1-inch mounds onto baking sheet. Using fingertip or a pastry brush, lightly coat top of each puff with some reserved egg.
Bake in preheated oven for 20 minutes, then reduce heat to 350 F and bake for 10 to 15 minutes longer until golden-brown. Immediately top each gougere with a few strands of reserved cheese. Return pans to oven to "set" cheese; it should take less than a minute. Serve warm. Gougeres can be baked, then frozen in plastic freezer bags for up to a month. When you're ready to reheat, place them frozen on baking sheets at 325 F for 5 minutes.
Makes about 36 small puffs.
— Recipe adapted by the Minneapolis Star Tribune from "The Art & Soul of Baking" from Sur La Table.
VARIATIONS: Replace Gruyere and mustard with 1/2 cup blue cheese and 1/3 cup finely chopped walnuts; or 1/2 cup crumbled, fresh goat cheese and 2 tablespoons chopped, fresh chives or dill (sprinkle tops with some grated Parmesan); or 1 cup cheddar cheese and 1 tablespoon finely chopped, fresh rosemary; or 1/2 cup crumbled, fresh goat cheese, zest of 1 lemon and some chopped, fresh parsley.