Potato, Leek and Radish Green Vichyssoise

• MAKE-AHEAD

Ingredients

1. 2 tablespoons unsalted butter
2. 2 medium leeks, white and tender green parts, coarsely chopped
3. 1 1/4 pounds Yukon Gold potatoes, peeled and cut into 1/2-inch dice
4. Salt and freshly ground pepper
5. 1 quart chicken stock or low-sodium broth
6. 1 quart water
7. 8 cups packed radish greens (from 2 pounds radishes)
8. 1 cup crème fraîche
9. 3 tablespoons finely chopped chives

1. Melt the butter in a large saucepan. Add the leeks and potatoes, season with salt and pepper and cook over moderately low heat, stirring occasionally, until the leeks are softened, about 8 minutes. Add the chicken stock and water and bring to a boil over high heat. Reduce the heat to moderately low and simmer until the potatoes are tender, about 15 minutes. Add the radish greens and crème fraîche and simmer for 2 minutes longer.
2. Working in batches, puree the soup in a blender on low speed until smooth and flecked with bits of green. Transfer to a large bowl, season with salt and pepper and refrigerate, stirring occasionally, until chilled, about 1 hour. Ladle the chilled soup into bowls, top with the chives and serve.