Place each chicken breast half between 2 sheets of heavy-duty plastic wrap; flatten to 1/4-inch thickness, using a meat mallet or rolling pin. Dredge chicken in breadcrumbs. Spoon 1 tablespoon of cheese onto each piece of chicken, and fold chicken in half. Place folded breast halves in an 8-inch square baking dish coated with cooking spray. Drizzle margarine over chicken. Bake at 400° for 25 minutes or until done.
Combine spinach and basil in a bowl, and drizzle with vinegar and oil. Sprinkle pepper over salad; toss well. Serve chicken over salad.