Wash and clean the chicken hearts. If they're large, it's best to cut them in 2.
Put the washed hearts in a colander to drain away the water.
Heat the oil in a pan. Roll each heart in flour and put it in the pan. Fry under a lid on moderate heat, turning them over once.
Sprinkle the ready hearts with black pepper and salt.
Put thin slices of butter on top of the warm chicken hearts.