Total time: 1 hour, 10 minutes, plus chilling time for the soup
Servings: This makes a scant 2 quarts soup
Note: This recipe calls for the use of a chinois, a very fine strainer; chinois are available at cooking and restaurant supply stores, as well as online. This recipe also calls for a juicer; juicers are generally available at home and kitchen supply stores, as well as online (the Test Kitchen tested the recipe using a blender instead of a juicer, and passed the purée through a strainer). Keller suggests serving the soup garnished with basil crème fraîche or cherry tomato confit.
1/2 cup chopped shallots, cut into large dice
1/2 cup chopped leeks, cut into large dice
1 cup chopped onions, cut into large dice
1 tablespoon butter
2 1/2 cups peeled, chopped baking potatoes, cut into large dice
1 quart water, or as needed
1 1/2 cups heavy cream
3 tablespoons crème fraîche
3 tablespoons mint leaves
1. In a large pot, sweat the shallots, leeks and onions in butter until completely soft. Add the diced potatoes and enough water to cover. Bring the water to a simmer and cook until the potatoes are tender. Add the cream and simmer an additional 20 minutes.
2. Transfer the soup in three batches to a blender and purée, adding one tablespoon of crème fraîche to each batch. Once puréed, pass the soup base through a fine chinois into a bowl, then cover and refrigerate until chilled.
3. Taste each cucumber to ensure that there is no bitter flavor. Cut the cucumbers into chunks, combine with mint leaves and then pass through a juicer; you should have at least 1½ cups juice (save any extra for another use). When the soup base is completely chilled, combine it with the 1½ cups cucumber juice and season to taste.
Each of 8 servings: 233 calories; 3 grams protein; 14 grams carbohydrates; 2 grams fiber; 19 grams fat; 12 grams saturated fat; 68 mg cholesterol; 2 grams sugar; 27 mg sodium.