1In 12-inch skillet, cook beef over medium heat, stirring occasionally, until brown; drain. In 3 1/2- to 4-quart slow cooker, place beef. Stir in refried beans, enchilada sauce, taco seasoning mix and salsa.
2Cover and cook on Low heat setting 4 to 6 hours.
3To serve, fill each bun with about 1/3 cup beef mixture and top with cheese, lettuce, tomato and sour cream.