This is a classic vegetable winter warmer in the Czech Republic and Slovakia. Potatoes and other root vegetables are incorporated in all kinds of recipes because they are inexpensive and easily available.
Soak the dried mushrooms in water to cover for about 20 minutes before you begin cooking.
Melt half the butter in a large pan and gently fry the onion, carrots, celeriac and leek for 5-10 minutes or until they are light golden. Add salt and pepper, and 1.5 litres/2½ pints/6¼ cups of boiling water.