Cook a lean beef roast in the crock pot until it starts to shred (approximately 6 hours on low heat). Remove fat and cut into approx. 1 x 1/2 inch pieces or chunks (don't shred). Melt butter and add olive oil to a large frying pan. Cook onions for 5 minutes over med. heat. Add mushrooms and cook for 10 more minutes (or until onions are transparent. Add beef drippings and heat.
Stir flour to mixture and cook for 1 minute. Gradually add beef broth and stir until thickened. Add salt, pepper, catsup, garlic powder, and worcestershire sauce and blend well. Heat until mixture starts to bubble. Lower heat to low.
Add sour cream and blend well. Add beef chunks. Do not boil! Heat very slowly over low heat. Fold mixture carefully so that meat does not shred too much (would cause the sauce to be thick with shredded meat rather than saucy). Heat for about 15 minutes over very low heat. Serve over medium wide or wide egg noodles.
If the sauce gets too thick, thin with cream, half n half, or milk.