EVER SINCE SETTLERS IN THE FIRST SOUTHERN colonies churned butter derived from a sour milk called
clabber and drank the leftover nutritious liquid, buttermilk has had a special status in the South that few outsiders appreciate. Gone are the days, however, when you can find natural buttermilk like that I drank as a child. Today it is replaced by the very respectable commercial product made from low-fat milk transformed with special bacteria. For centuries, buttermilk has been a vital ingredient in the making of certain biscuits, cornbreads, hush puppies, pies,
puddings, spoonbreads, marinades, and salad dressings, but it’s also the major ingredient in any number of tangy soups, such as this one, which is just as good chilled as hot. Fresh parsley can be substituted for the watercress, and if you want to produce a really modern soup, use arugula leaves.

Makes 4 servings

INGREDIENTS

• 1 large bunch fresh watercress, rinsed and stems removed
• 1 tablespoon butter
• 1 large onion, chopped
• 1 garlic clove, minced
• 1 medium potato, peeled and cubed
• 3 cups chicken broth
• Salt and freshly ground black pepper to taste
• 3⁄4 cup buttermilk
• Cayenne pepper to taste

INSTRUCTIONS

1. Tear off about 1⁄2 cup of watercress leaves for garnish and set them aside.
2. In a saucepan, melt the butter over moderate heat.
3. Add the chopped onions and minced garlic to the saucepan and stir until they become soft, approximately 2 minutes.
4. Add the cubed potatoes, chicken broth, salt, and black pepper to the saucepan and bring the mixture to a boil.
5. Add the remaining watercress to the saucepan, slightly reduce the heat, cover the saucepan, and simmer until the potatoes are tender, about 15 minutes.
6. While the soup is simmering, bring about 2 cups of water to a boil.
7. Add the reserved watercress leaves to the boiling water and blanch them for 10 seconds.
8. Drain the blanched watercress leaves and set them aside.
9. Pour the potato-and-watercress mixture from the saucepan into a blender or food processor and blend until smooth.
10. Return the blended mixture to the saucepan.
11. Add the buttermilk, cayenne pepper, and blanched watercress leaves to the saucepan.
12. Heat the soup thoroughly.
13. Serve the watercress soup hot or warm in soup plates, garnishing each serving with the reserved watercress leaves.