Preheat the oven to 350°F.

If the rigatoni is not already cooked, cook 8 ounces whole-wheat rigatoni in boiling water according to package directions until al dente; drain well.

In a large bowl, combine the cooked rigatoni, 3/4 of the 24-ounce jar of spaghetti sauce, and 3/4 cup shredded part-skim mozzarella. Stir until the pasta is evenly coated.

Spread the pasta mixture in an even layer in the bottom of a deep-dish baking pan.

Arrange the 4 boneless, skinless chicken breasts (either whole or cut into cubes, as preferred) in a single layer on top of the pasta.

Spoon the remaining 1/4 of the jar of spaghetti sauce over the chicken, then sprinkle 1/4 cup shredded Parmesan evenly over the top.

Bake uncovered for 30 minutes, or until the chicken is cooked through (no pink in the center; internal temperature 165°F if using a thermometer) and the cheese is melted.

Remove from the oven and let rest a few minutes before serving.