Preheat the oven to 450°F (230°C) and lightly spray a 9×9-inch baking pan with nonstick cooking spray.
Slice each chicken breast lengthwise so you have 4–6 ounce pieces (about 2–4 pieces total depending on breast size).
Combine the breadcrumbs and grated Parmesan in a shallow dish and stir to mix evenly.
Coat each chicken piece thoroughly in the breadcrumb mixture, pressing gently so the crumbs adhere, and place the pieces in the prepared baking pan in a single layer.
Bake the chicken uncovered for 15–20 minutes, until the coating is golden and the chicken is mostly cooked through.
Remove the pan from the oven, spoon about 1 cup of pasta sauce evenly over the chicken pieces, then sprinkle the shredded mozzarella on top.
Return the pan to the oven and bake an additional 5–10 minutes, until the cheese is melted and the chicken reaches a safe internal temperature.
Serve the chicken over cooked pasta if desired, or alongside a salad for a lower-carb option.