Preheat oven to 400 degrees F. Spray a baking sheet with cooking spray.
Bring a large pot of salted water to a boil. Once water is boiling, add pasta and cook according to package directions for al dente. Drain.
Meanwhile, stir together Panko crumbs, Parmesan, salt and pepper in a shallow dish or pie plate. In a second dish, whisk together the egg and milk or water. Dip each chicken piece first into the egg and then into the crumb mixture, so that both sides are coated. Place on the prepared baking sheet.
Bake chicken in upper third of the oven for 12-15 minutes, until it registers 165 on an instant-read thermometer. Remove from oven and turn on the broiler.
Spoon ¼ cup marinara sauce over each piece of chicken, and then sprinkle each with ¼ cup of mozzarella cheese. Return the chicken to the oven and broil for 2-3 minutes, until cheese is melted.
Divide cooked pasta between four plates, top with the remaining marinara sauce and chicken. Sprinkle on fresh parsley. Serve.