In a medium saucepan, combine chicken, soup, green beans, mushrooms, cheese and mayonnaise. Heat until hot and bubbling. Pour hot mixture into an ungreased 2 litre baking dish. Separate biscuits and arrange over chicken mixture. Brush biscuits with melted butter; sprinkle with bread crumbs. Bake in a preheated 375 degree oven for about 30 minutes, or until golden brown. Serve immediately.