Place cooked chicken in an oven-safe dish, and cover with marinara.
Top chicken with slices or grated mozzarella. Bake at 350 degrees until the sauce is bubbling and the cheese is lightly browned - about 10-15 minutes.
While the chicken is cooking, fill a large pot with water, add 1 tsp of kosher salt, 2 tsp of olive oil. Bring to a boil, and add dry spaghetti noodles. Cook until al dente, about 6-8 minutes.
Once the chicken is done, sprinkle with panko breadcrumbs, and put under a low broiler for 1-2 minutes, or until the panko is browned. Serve on top of spaghetti noodles.