Cook rigatoni according to package direction. Drain; set aside. Heat oven to 350 degrees. Meanwhile, in 3-quart saucepan melt butter; stir in mushrooms and onion. Cook over medium-high heat, stirring constantly, until onion is soft (2 to 3 minutes). Reduce heat to medium; stir in flour until smooth and bubbly (1 minute). With wire whisk stir in half-and-half and broth and cook, stirring occasionally, until sauce thickens (4 to 5 minutes). Remove from heat. Stir in 1/2-cup Parmesan cheese and all remaining ingredients. Spoon cooked rigatoni into 3-quart casserole. Add sauce; stir gently to coat. Cover; bake 15 minutes. Stir; sprinkle top with remaining 1/4-cup Parmesan cheese. Cover; continue baking for 10 to 15 minutes or until heated through.