Estonian Chilled Cucumber Soup

Description
Make sure it's thoroughly chilled before serving and follow it with the Estonian Cod Salad with Horseradish Sauce for a hot weather luncheon.

Ingredients

 * 2 tablespoons unsalted butter
 * 1 small Onion, finely chopped
 * 7 medium-size firm Kirby cucumbers, peeled, seeded, and grated
 * 1 cup chopped fresh dill
 * 3 cups chicken stock or canned broth
 * salt (to taste)
 * Freshly ground white pepper (to taste)
 * 1 cup sour cream
 * 3 large egg yolks
 * 1/4 cup dry sherry
 * Grated zest of 1 lemon

Directions
1.	Melt the butter in a pan over medium heat.

2.	Add the Onion and fry it until softened but not colored, about 5 minutes.

3.	Stir in the cucumbers and 1 cup dill, and leave it until the cucumber has softened, 5 to 7 minutes.

4.	Gradually stir in the stock. Bring to a boil, and then reduce the heat to low. Add salt and pepper and simmer, covered, for 5 minutes.

5.	Puree the soup in a food processor until smooth. Return to the pot and simmer for 2 minutes, then remove from the heat.

6.	In a bowl, whisk the sour cream with the egg yolks until blended.

7.	Stir in 1 cup of hot soup, then whisk the mixture back into the pot, stirring vigorously until smooth.

8.	Now add the lemon juice; then add more salt or freshly ground white pepper, if you wish.

9.	Cool and refrigerate the soup for at least 4 hours.

Serving:

stir the soup before serving. Serve garnished with dill. Serving will be enough for 4 to 6.