I got this from the Canada Bargain Hunters board. (Baby Center)
1 pkg egg noodles
1 lb ground beef
12 oz sour cream
1 can cream of mushroom soup
1 onion (or 2 tsp onion powder)
Sliced mushrooms (fresh, jarred, or canned)
Cook egg noodles and drain.
Brown ground beef.
Add onion powder.
Add sour cream, soup, and mushrooms. Stir till hot.
Mix with noodles.