Preheat oven to 450°F and spray a 9×9-inch baking pan with nonstick cooking spray.
Slice the 1 pound boneless skinless chicken breasts lengthwise into pieces about 4–6 ounces each, aiming for even thickness so they cook evenly.
In a shallow dish, combine ¾ cup breadcrumbs and ¼ cup grated Parmesan; stir to mix.
Working one piece at a time, press each chicken piece into the breadcrumb mixture, coating and pressing the crumbs firmly onto both sides so they adhere. Arrange the coated pieces in a single layer in the prepared pan.
Bake uncovered for 15–20 minutes, until the breadcrumb coating is golden and the chicken is mostly cooked.
Remove the pan from the oven. Evenly spoon 1 cup pasta sauce over the chicken pieces, then evenly sprinkle 1 cup 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 is cooked through (165°F internal temperature).
Serve the chicken over cooked pasta if desired (cook pasta according to package directions), or serve with a salad for a lower-carb option.