1

Bring the milk, butter, mustard, salt, and pepper to a boil in a medium saucepan; reduce the heat to medium. Beat in the flour and Parmesan cheese with a wooden spoon, stirring vigorously, until the mixture leaves the side of the pan. Cool for 10 minutes.

2

Adjust the racks to divide the oven into thirds; preheat the oven to 400ºF. Line two baking sheets with foil and lightly coat with nonstick spray.

3

With an electric mixer on medium speed, beat the eggs into the flour mixture until well blended. Sift in the baking powder, then add the egg whites and continue beating until the mixture is glossy and smooth. Beat in the cheddar cheese on low speed until just combined.

4

Spoon the mixture into a pastry bag or a plastic food-storage bag with a corner cut off. Pipe into 1-inch mounds, spacing 1 inch apart. (You can also pipe the mixture into 1 1⁄2-inch-long “fingers” if you prefer.) You should have about 75 puffs or fingers. Bake until golden brown and firm to the touch, 22 minutes. Serve hot or warm. Yields 5 puffs per serving.