Melt butter in heavy skillet and saute onion until soft. Add ground beef and garlic and cook until beef is brown. Stir in flour, salt, pepper and mushrooms and cook five minutes. Add soup and simmer 10 minutes. Stir in sour cream and heat just until warm.
Notes
You can prepare all except adding the soup and sour cream before you leave home. Mixture can be cooled and put in a resealable bag, then finished at the campsite.
