4ouncespepperoni and/or sausage cut into small pieces (about 1 cup)
Preheat oven to 375 F. Grease a 24-cup mini muffin pan. In a large bowl, whisk together the flour and baking powder; whisk in the milk and egg. Stir in the mozzarella and pepperoni and/or sausage; let stand for 10 minutes.
Stir the batter and divide among the mini-muffin cups. Bake until puffed and golden, 20 to 25 minutes.