Spread olive oil into the bottom of your slow cooker.
In a small bowl, whisk the egg until beaten.
In a medium bowl, mix the bread crumbs, Parmesan cheese, pepper and salt together in a medium bowl.
Dip the chicken into the egg, then into the bread crumb mixture, coating both sides with egg and bread crumb mixture.
Place the chicken breast pieces in the bottom of the slow cooker.
Sprinkle mozzarella cheese on top.
Cover chicken and cheese with entire jar of marinara sauce.
Close lid and cook on High for about 3-4 hours or until chicken is done.
Serve with your favorite pasta.