1 tablespoon unsalted butter, 3/4 cup cleaned and sliced leek (white part only), 12 ounces peeled and diced Yukon Gold or russet potatoes (about 2 cups), 2 cups chicken stock, preferably home-made, 2 cups heavy cream, sea salt and freshly ground pepper to taste, 1 tablespoon fresh chives, chopped, 2 ounces black caviar.
Melt the butter in a saucepan over medium heat. Add the sliced leek and cook for 3 – 5 minutes until tender but not browned. Add a small amount of water if the leeks begin to brown at all. Add the potatoes and cook for a few minutes, but do not allow them to brown. Add the chicken stock and simmer about 20 minutes or until the potatoes are very tender. Add the cream and return to a simmer. Remove the soup from the stove and let cool for about 30 minutes. Puree the soup in a food processor until very smooth, then strain through a fine mesh sieve. Remember that the soup will continue to thicken as it cools. Season the soup to taste with salt and pepper then refrigerate the soup until well chilled. If the soup is too thick, whisk in some milk or cream. Serve the soup in chilled bowls. Sprinkle the soup with the finely sliced chives and garnish with a large dollop of caviar.