This is my friend Shelly's recipe. It's something she's made since we were in college, and it's good comfort food.
1 large round steak, cut into bite-size pieces
1-2 cans mushroom pieces
2 cans cream of mushroom or celery soup
1 box onion soup mix
16 oz. sour cream
Mix all ingredients in slow cooker except sour cream and noodles. Cook at 375ºF for two hours. Add sour cream and cook another 30 minutes. Serve warm over cooked egg noodles.