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.
Combine breadcrumbs, Parmesan cheese, Italian seasoning, and pepper in a shallow dish. Dredge 1 chicken breast half in flour. Dip in egg whites; dredge in breadcrumb mixture. Repeat procedure with remaining chicken, flour, egg whites, and breadcrumb mixture.
Heat oil in a large nonstick skillet over medium-high heat. Add chicken; cook 5 minutes on each side or until done.
Place 1 cup spaghetti in each of 4 gratin dishes. Spoon 1/2 cup Ultimate Quick-and-Easy Pasta Sauce over each serving. Top each with 1 chicken breast half. Spoon 1/4 cup sauce over each serving. Sprinkle each serving with 1/4 cup mozzarella cheese.
Preheat broiler. Place gratin dishes on a baking sheet; broil 3 minutes or until cheese melts. Garnish with basil sprigs, if desired.