• 1/2 oz. dried porcini (or similar) mushrooms
• 1 chopped celeriac (3-4 oz.)
• 1 chopped onion
• 2 oz butter
• 1/4 pt. sour cream
• 1/4 pt. regular cream or half and half
• 1 Tbs flour
• dill weed or parsley
• salt and pepper

Soak the mushrooms in a ladle of very hot water for 20-30 minutes.  While they are soaking, sweat the celeriac and onion in the butter in a covered pan until they begin to soften.  Add the mushrooms and their liquor.  Simmer, covered, until the vegetables are tender.  Puree in a blender and return the puree to the pan.  Mix the creams and the flour to make a smooth paste and stir into the soup as it reheats.  Cook slowly for about five minutes, until the taste of flour has gone.  If the soup is too thick for your taste, dilute with hot water.  Stir in chopped dill weed, salt and pepper to taste.  Serve with croutons.

From Jane Grigson’s Vegetable Book.