Melt half of butter in large skillet over medium high heat. Add mushrooms and onions and saute until tender, about 5 to 10 minutes. Remove and keep warm. Melt remaining butter in same skilled over medium high heat. Sprinkle chops with rosemary, garlic powder and salt and pepper. Add to skillet and saute until browned on both sides about 5 minutes. Reduce heat to medium and continue cooking until tender. Transfer lamb chops to heated platter. Pour wine into skilled and cook over medium high heat, scraping up any browned its clinging to bottom of pan, until liquid is reduced by about 1/3. Spoon vegetables over chops and top with sauce.