Cook bacon in a large skillet over medium heat until crisp, about 5 minutes per side. Transfer to paper towels to drain. Pour off fat into a bowl. Wipe skillet clean with a paper towel; set aside.
Stir together cheese, sour cream, bell pepper, scallions, flour, mustard, 1/2 teaspoon salt, 1/4 teaspoon pepper, cayenne, and egg yolks in a large bowl; set aside. In another large bowl, beat egg whites until stiff peaks form. Fold beaten egg whites into reserved batter.
Heat 2 tablespoons reserved fat (or vegetable oil) in skillet over medium heat until hot but not smoking. Working in batches of 3 or 4, pour 2 tablespoons batter into skillet for each cake; cook, turning once, until crisp, 8 to 10 minutes (add more fat or oil if skillet seems dry). Season with salt and pepper. Serve hot with reserved bacon.