Roughly chop 2 leaks and slice 3 potatoes. Heat 1 tbsp butter in a pan and add chopped leaks, few thyme sprigs and sauté. Add sliced potatoes, 1 cup vegetable stock, ½ cup milk and mix. Season it with cracked white pepper and simmer till potatoes are cooked. Add 1 tbsp cream, salt and boil for 1 minute. Cool the mixture and blend it into smooth puree. Pour the soup into a cup and garnish it with chopped chives and cracked black pepper. Vichyssoise Soup is ready.