Separate whites from yolks, setting yolks aside. With a mixer, whip whites until stiff peaks form. (If using crumbled bacon, fold in now). Spoon into 4 clouds on parchment-lined baking sheet. With a spoon, make a deep well in the center of the clouds. Bake on 450 degrees for 3 minutes, then add 1 yolk to each cloud. Season with salt and pepper. Return to oven and bake until yolks are set (approximately 2 – 3 minutes).