There's nothing more comforting on cold winter nights than mashed potatoes . And now a top celebrity chef has revealed his best tips for perfecting the dish - and the most common mistakes we make when cooking it. MasterChef host Marcus Wareing , who ran Michelin-starred restaurant Marcus Belgravia in The Berkeley, shared his mash method in his book Marcus Everyday. A British dinner staple, mash is usually served as a side dish to meat or vegetables and can be made using peeled or unpeeled