Combine the first 4 ingredients in a shallow dish. Dredge each piece of chicken in the flour mixture. Dip each piece of chicken in egg whites; dredge in cornflakes.
Arrange chicken in a 13 x 9-inch baking dish coated with cooking spray. Bake at 350° for 25 minutes or until crisp.
Place spaghetti sauce in a medium saucepan, and cook over medium heat until thoroughly heated. Pour sauce over chicken, and sprinkle with cheese. Bake an additional 5 minutes or until cheese melts.