Slice and wash 2 large leeks, peel and dice 3 large potatoes. Sautee leeks, garlic and celery, then add the potatoes, some mustard and a litre of stock. I also stirred in a teaspoon of vegemite and a splosh of worcestershire sauce. Season. Simmer until veg is soft, liquidise in blender or using stick blender. Stir in chopped chives. Serve with natural yogurt and parsley.