1Place mushrooms in 2 1/2- to 3 1/2-quart slow cooker. Mix butter, sherry, half-and-half, garlic and soup mix (dry) in small bowl. Stir soup mixture gently into mushrooms to coat.
2Cover and cook on High heat setting 2 to 3 hours or until mushrooms are tender and hot.
3Gently stir sour cream into mushrooms. Sprinkle with parsley before serving. Mush-rooms will hold on Low heat setting up to 2 hours; stir occasionally.