Ocado Family Pack Chestnut Mushrooms. Chestnut Mushrooms have a light brown to caramel coloured cap with white, off white, pink stalk. Chestnut Mushroom Casserole: - Add washed quartered chestnut mushrooms to fried onion, garlic chunks of aubergine and butter beans. - Add a touch of paprika, tomato ketchup, muscovado sugar and some veg stock. Cover and simmer until beans are softened and a sauce has formed. - Serve with warmed flat bread.