Spray an 8-by-8 inch baking dish with butter-flavored spray.
In a large skillet sprayed with butter-flavored spray, saute dried beef and onion for 5 minutes.
In a covered jar, combine skim milk and flour. Shake well to blend. Add milk mixture to beef mixture. Mix well to combine.
Stir in cream cheese. Continue cooking for 5 minutes or until mixture starts to thicken. Stir in mushrooms, cheddar cheese, and parsley flakes. Add noodles and peas. Mix well to combine. Pour mixture into prepared baking dish.
Bake for 25 to 30 minutes. Place baking dish on a wire rack and let set for 5 minutes.