In a large skillet, melt butter and add vegetable oil. Add new potatoes and onions; sprinkle liberally with salt. Season to taste with pepper. Cover pan with a paper towel and lid. Cook, turning occasionally over medium heat until potatoes and onions are browned and tender, about 25 to 30 minutes. Serve with prime rib with Yorkshire pudding and onion-mushroom gravy, steamed brussel sprouts and red wine such as Beaujolais . Yield: 4 servings.