Heat oven to 425 degrees. Spray 24 mini muffin cups with nonstick cooking spray.
Combine milk, egg and egg white. Beat with a wire whisk. Add flour and beat until smooth. Stir in cheese.
Place pan on cookie sheet in oven for several minutes to heat. Remove cookie sheet from oven and quickly add batter evenly into hot muffin cups. Fill about 2/3 full.
Bake for 18 minutes or until popovers are puffed and golden brown.
Best served warm. To reheat pop in microwave for 15 seconds.