1Heat oven to 350°F. Spray 11x7-inch (2-quart) glass baking dish with cooking spray.
2Cook and drain spaghetti as directed on package; set aside. In 12-inch skillet, heat oil over medium-high heat until hot. Cook onion in oil 2 to 3 minutes, stirring frequently, until almost tender. Stir in soup, half-and-half, salt and pepper; heat to boiling. Stir in chicken and cooked spaghetti. Pour mixture into baking dish.
3Cover with foil; bake 20 minutes. In small bowl, mix Topping ingredients; sprinkle over pasta mixture. Bake uncovered about 10 minutes longer or until bubbly around edges and center is hot.