How to Make It
Coat a large nonstick skillet with cooking spray, and place over medium heat until hot. Add mushrooms and next 3 ingredients; sauté for 6 minutes or until tender.
Combine milk and next 6 ingredients in a bowl; stir well. Add mushroom mixture, noodles, and next 3 ingredients; stir gently.
Spoon noodle mixture into a shallow 2-quart casserole coated with cooking spray. Cover and bake at 350° for 40 minutes.
Combine the breadcrumbs, Parmesan cheese, and margarine in a small bowl; stir well, and sprinkle over casserole. Bake, uncovered, at 350° for 10 minutes.
Make-Ahead Tips: You can assemble the casserole up to 4 hours ahead of time, omitting breadcrumb mixture; cover and chill. Let stand at room temperature 30 minutes before baking. Top with breadcrumb mixture during last 10 minutes of baking.