Timballo Spaghetti Casserole

Name: Timballo Spaghetti Casserole
Prep time: 20 min
Cook time: 40 min
Total time: 1 h
Cuisine: European, Italian, Mediterranean
Ingredients: 1 tablespoon olive oil; 1 (16 ounce) package spaghetti; 2 (24 ounce) jars marinara sauce; 3 cups cooked chicken breast meat, diced; 1 large onion, diced; 1 (7 ounce) package of sliced pepperoni, diced; 1 green pepper, diced; 1 (5 ounce) can mushroom pieces, drained; 1 (3 ounce) can sliced black olives, drained; 3 cups shredded mozzarella cheese; 1 tablespoon grated Parmesan cheese, or to taste