• 1 Lbs. celeriac, cut into cubes
• 2 Tbs. lemon juice
• 1 onion\cooked, chopped, extra
• 2 potato, chopped
• 4 cup vegetable stock
• 1 bouquet garni
• salt and pepper
• 1/4 cup nonfat yogurt
• 1-3/4 oz. butter
• 1 onion\cooked, chopped, extra
• 1-1/2 oz. breadcrumbs
• 3 Tbs. chopped walnuts
• 2 tsp. celery seed

Toss the celeriac in a small bowl of water with the lemon juice. Place them in a pan with the onion and potatoes, add the stock and bouquet garni and bring slowly to the boil. Cover the pan and simmer for 30 minutes. Discard the herbs and process the soup in a food processor or blender to make a smooth purée. Season to taste with salt and pepper and stir in the yogurt. Reheat gently. To make the topping, melt the butter and fry the extra onion for 2-3 minutes. Stir in the breadcrumbs and walnuts and stir-fry until they are dry and golden. Stir in the celery seeds. Scatter over the soup just before serving.