Preparation Soak liver in milk in a bowl 20 minutes. While liver is soaking, cook bacon in a 12-inch nonstick skillet over moderate heat, turning over occasionally, until crisp. Transfer bacon to paper towels to drain and reserve 2 1/2 tablespoons fat in skillet, transferring remaining fat to a small bowl. Cook onions with salt and pepper to taste in fat in skillet over moderate heat, stirring frequently, until golden brown, 12 to 15 minutes. Transfer onions to a bowl and add bacon. Keep warm, covered. Pat liver dry and discard milk. Stir together flour, salt, and pepper on a sheet of wax paper and dredge liver in flour mixture, shaking off excess. Add 1 1/2 tablespoons reserved bacon fat to skillet and heat over moderately high heat until hot but not smoking, then sauté liver, turning over once, until browned but still pink inside, about 4 minutes total. Serve liver topped with onions and bacon.
Preparation Soak liver in milk in a bowl 20 minutes. While liver is soaking, cook bacon in a 12-inch nonstick skillet over moderate heat, turning over occasionally, until crisp. Transfer bacon to paper towels to drain and reserve 2 1/2 tablespoons fat in skillet, transferring remaining fat to a small bowl. Cook onions with salt and pepper to taste in fat in skillet over moderate heat, stirring frequently, until golden brown, 12 to 15 minutes. Transfer onions to a bowl and add bacon. Keep warm, covered. Pat liver dry and discard milk. Stir together flour, salt, and pepper on a sheet of wax paper and dredge liver in flour mixture, shaking off excess. Add 1 1/2 tablespoons reserved bacon fat to skillet and heat over moderately high heat until hot but not smoking, then sauté liver, turning over once, until browned but still pink inside, about 4 minutes total. Serve liver topped with onions and bacon.