4 large leeks (white bulbs only)
2 tablespoons cider vinegar
1/4 cup (1/2 stick) unsalted butter
1 onion, thinly sliced
4 Yukon Gold potatoes (about 1/2 pound each), peeled and thinly sliced
4 cups defatted chicken broth, preferably homemade
2 teaspoons fresh lemon juice
1-1/2 cups milk
2-1/4 cups heavy (or whipping) cream
Salt and freshly ground black pepper, to taste
6 teaspoons American golden caviar, for garnish
1 bunch fresh chives, snipped, for garnish
1/2 cup sour cream, for garnish
Trim the roots from the leeks, and cut a 1-1/2-inch deep "X" through the top and bottom ends of each bulb. Place the leeks in a bowl, add the vinegar, and cover with cold water. Let soak for 20 minutes to remove any sand from the leeks. Drain, and rinse well under cold water. Thinly slice the leeks crosswise.
Melt the butter in a heavy soup pot over medium-low heat. Add the leeks and onion. Cook, stirring occasionally, until wilted, about 15 minutes. Add the potatoes, chicken broth, and lemon juice, and bring to a boil. Then reduce the heat to medium and simmer for 20 minutes. Partially cover the pot and simmer, stirring occasionally, 20 minutes more. If the soup boils, further reduce the heat. Remove it from the heat and let it cool to room temperature.
Process the soup, in batches, in a blender or food processor, pulsing the machine on and off so that some texture remains. Return it to the pot, and add the milk and 1-1/2 cups of the cream. Season generously with salt and pepper, and heat over medium heat just to a simmer. Do not boil. Remove from the heat and cool to room temperature. Refrigerate, covered, overnight.
The following day, stir in the remaining 3/4 cup cream. Cover and return to the refrigerator until ready to use. Serve chilled or hot, garnished with caviar, chives, and a dollop of sour cream.
Yield: 6 servings