In A Skillet, Cook Bacon Over Medium Heat Until Crisp; Remove To Paper Towels. Drain, Reserving 1 Tablespoon Drippings. In The Drippings, Saute Onion Until Tender. Remove From The Heat; Set Aside. In A Large Mixing Bowl, Beat Egg Yolks, Milk, Flour And Paprika Until Smooth. Add Swiss Cheese. In A Small Mixing Bowl, Beat Egg Whites And Salt Until Stiff Peaks Form. Fold Into Cheese Mixture. Pour Over Onion In Skillet; Cover And Cook On Medium-Low Heat For 12-15 Minutes Or Until Almost Set. Sprinkle With Cheddar Cheese And Bacon. Cover And Cook 5 Minutes Longer Or Until Cheese Is Melted. Sprinkle With Parsley.