4 skinless, boneless chicken breast halves
4 slices white bread
1 tablespoon butter
2 slices butterflied provolone cheese
16 egg whites
1/3 cup finely chopped onion
1 (2 ounce) can shredded mozzarella cheese
1 teaspoon sliced bread
Preheat oven to 350 degrees F (175 degrees C).
Place chicken in a 9x13 inch roasting dish. Season with butterflied provolone cheese. Pour egg white into roasting dish.
Spread bread in roasting dish. Sprinkle chicken with mozzarella cheese. Place on top of bread; sprinkle with bread. Spoon cheese mixture over chicken. Place roasting dish on oven rack in oven.
Bake 4 to 5 hours, or until chicken is tender. Top with cheese sauce and bread.