Preheat oven to 400°. In a large skillet, cook bacon over medium heat until crisp, stirring occasionally. Remove with a slotted spoon; drain on paper towels. Allow drippings to cool for 30 minutes. Reserve 1/3 cup drippings (discard remaining or save for another use).
Sift flour, sugar, baking powder and salt together. In a KitchenAid Stand Mixer using the Flat Beater Accessory, combine milk and egg. Gradually add warm (not hot) bacon drippings. Mix in flour mixture just until moistened. Stir in cheeses and bacon.
Fill 12 greased muffin cups three-fourths full. Bake until a toothpick inserted in center comes out clean, 15-17 minutes. Cool 5 minutes before removing from pan to a wire rack. Serve warm.
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