Heat oven to 350°F. Spray 11x7-inch (2-quart) glass baking dish with cooking spray. Cook and drain spaghetti as directed on package; set aside.
Meanwhile, in 10-inch skillet, heat 2 tablespoons olive or vegetable oil over medium-high heat until hot. Cook onion in oil 3 to 5 minutes, stirring frequently, until almost tender. Stir in cooking sauce, half-and-half, 1/2 teaspoon salt and 1/4 teaspoon pepper; heat to boiling. Carefully stir in chicken and spaghetti. Pour mixture into baking dish.
Cover with foil; bake 20 minutes. In small bowl, mix Topping ingredients; sprinkle over pasta mixture. Bake uncovered 10 minutes longer or until bubbly around edges and center is hot.