SPINACH SOUP

SPINACH SOUP `This can be the best soup in the world if the spinach isn't overcooked,' writes Joyce Goldstein. `Use as little stock as necessary to cook the leaves; puree the soup quickly. Then thin the soup, while still hot, to the desired consistency. This way, the spinach will retain its bright green color.' 4 tablespoons unsalted butter 2 medium onions, sliced (about 2 cups) 1 russet potato, peeled and thinly sliced 2 to 3 cups chicken stock 10 to 12 cups loosely packed, trimmed spinach leaves (about 6 bunches), rinsed well and drained Salt and freshly ground pepper Pinch freshly grated nutmeg About 1/4 cup heavy cream if needed

Melt the butter in a large, wide heavy saucepan over medium heat. Add the onions and cook until translucent, about 7 minutes. Add the potato and 1 1/2 cups chicken stock. Heat to boiling, then reduce heat and simmer until the potato is very soft.

Increase the heat to high. Start adding the spinach leaves by handfuls, pushing the leaves under the hot stock, until all of the spinach is submerged. Quickly heat to boiling, then remove from the heat. Using a slotted spoon, transfer about half the solids to a blender and puree. Pour into a bowl and puree the remaining solids.

Thin the soup - first with the hot stock in the pan, then with the remaining stock, also heated. Season to taste with salt, pepper, and nutmeg. If the spinach has an earthy or slightly bitter taste, add enough cream to smooth it. You may not need any cream at all if the spinach is young and sweet. Serves 6-8. From ``The Mediterranean Kitchen,'' copyright 1989 by Joyce Goldstein, reprinted with permission from William Morrow & Company, Inc. Fifth in a series. For a reprint of this series, send $3 with your name and address to: The Christian Science Monitor P-410, 1 Norway St., Boston, MA 02115. Discounts are available for quantity orders.