2 litres beef stock or vegetable stock
1 onion, peeled and chopped
1 bouquet garni
1 can mushrooms (or fresh)
3 uncooked medium-sized beetroot, peeled and sliced thickly
300 ml kwas
1 tsp sugar
Heat beef stock in a large pan. Add the onion, bouquet garni, mushrooms and beetroot. Boil for an hour. Strain the soup and stir in the kwas into the clear soup. Add sugar to taste and reheat, if necessary without boiling.