1 tablespoon vegetable oil
1 cup uncooked white rice
1 (8 ounce) can chopped pinto beans with juice
1/2 pound beef cubes
1 (8 ounce) container sour cream
1/4 cup chopped onion
1/4 cup chopped green bell pepper
1 (16 ounce) can whole fresh mushrooms, drained
2 tablespoons distilled white vinegar
1/4 cup butter
Heat oil in a large nonstick skillet over medium heat. Fry pinto beans for about 1 minute, or until they are golden brown and cooked through. Add enough water to cover by 2 inches of water in the pan. Cook, stirring, for 5 minutes. Add beef and rice and stir. Stirring occasionally, cook about 15 minutes. Reduce heat to medium-low and continue cooking for 5 minutes. Stir in cooked pinto beans and mushrooms, vinegar, and butter. Bring to a boil and boil for 5 minutes. Reduce heat to low and simmer for 5 minutes, stirring.