Tony Maws was experimenting with a vichyssoise for his restaurant staff meal when he decided to add radish greens. They made the cold soup so vibrant that Maws put the dish on his menu.Plus: More Soup Recipes and Tips
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.
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.
The soup can be refrigerated for up to 2 days.
A crisp, dry white or sparkling wine will contrast with the creamy soup and blend with the slightly bitter greens. Try a simple French vin de pays or an Italian Prosecco.