Lightly grease two baking sheets; set aside. In a medium saucepan, combine the water, butter, and salt. Bring to boiling. Add flour all at once, stirring vigorously. Cook and stir until mixture forms a ball. Remove from heat. Transfer to a large mixing bowl. Cool for 10 minutes. Add eggs, one at a time, beating with an electric mixer on medium speed for 1 minute after each addition. Stir in Gruyere cheese, mustard, white pepper, and the 1/8 teaspoon cayenne pepper.

Preheat oven to 400F. Using a pastry bag fitted with a 1/2-inch star tip, pipe batter in 1-inch mounds about 11/2 inches apart onto the prepared baking sheets. (Or use 2 teaspoons batter for each puff.)

Bake for 20 to 25 minutes or until puffed and golden brown. Serve warm. If desired, sprinkle with additional cayenne pepper. Makes about 60 gougeres.

Make-Ahead: Bake gougeres as directed. Cool on wire racks. Place cooled gougeres in an airtight container and store in the freezer up to 1 month. To reheat, place frozen gougeres on a baking sheet and bake, uncovered, in a preheated 350F oven for 6 to 8 minutes or until heated.