This chilled soup is traditionally garnished with fresh chives. We added the peppery snap of watercress and the tang of buttermilk to give it bite.

　　

Ingredients

serves 6

　　3 tablespoons unsalted butter

　　4 leeks, white and light green parts only, halved lengthwise and then thinly sliced into half-moons, washed well and drained

　　3 large white potatoes, peeled and cut into 1-inch pieces

　　4 1/2 cups homemade or low-sodium store-bought chicken stock

　　3 cups cleaned watercress leaves, loosely packed

　　Coarse salt and freshly ground white pepper

　　1 cup half-and-half

　　1 cup buttermilk

　　

Step 1

Melt the butter in a stockpot over medium-low heat. Add the leeks, and cook, covered, until tender, about 15 minutes.

　　

Step 2

Add the potatoes, stock, and 2 cups water. Bring to a boil; simmer until the potatoes are tender, about 20 minutes. Cool completely; stir in 2 cups of the watercress.

　　

Step 3

Working in batches, puree the soup in a blender until smooth. Transfer the pureed soup to a large bowl. Season with salt and white pepper. Stir in the half-and-half; chill at least 1 hour. Add the buttermilk just before serving. Adjust seasoning; if necessary, thin the soup with a bit more chicken stock or water to achieve the desired consistency. Garnish with the remaining cup watercress leaves.

　　Reprinted with permission from The Martha Stewart Living Cookbook: The New Classics by Martha Stewart Living Magazine, copyright © 2007. Published by Clarkson Potter, a division of The Crown Publishing Group.Buy the full book from Amazon.