Cut roast beef up into strips.
Heat beef in a large frying pan. (Add a little butter or oil if desired.) I have also added onion at this point too.
Pour the mustroom soup and mushrooms over beef. Continue to heat.
Add in ketchup, Worchestershire sauce, garlic powder and chili powder. Stir well.
When heated through and ready to serve, gently stir in sour cream.
Serve over mashed potatoes or wide egg noodles.