Cook With M&S Mushroom Medley Frozen Add this mix of white button, chestnut, nameko and shiitake mushrooms to dishes for a taste of the exotic. Pan-fry for seven to eight minutes with butter, garlic and soy sauce and serve with chopped spring onions. Or simply add from frozen to soups, stews, casseroles or pasta sauces. 1 of your 5 a day.