Until I began working on this book, I did what most cooks do: I bought beautiful radishes with bushy green tops and lopped off and discarded the tops. Never again. Radish tops are both edible and absolutely delicious, fresh or cooked. This recipe, based on a classic French potage, takes full advantage of the radish tops, delivering a brilliant green puréed soup with a silky texture and spicy, bright taste. Serve it in the traditional manner as a starter, or offer soup shots for a fun and unexpected appetizer.
2 tbsp unsalted butter
1 leek, white and light green part only, halved lengthwise and thinly sliced crosswise into half-moons
1 small yellow onion, diced
1 carrot, peeled and diced
11/2 tsp kosher or fine sea salt
1 medium russet potato, 61/2 oz/185 g, peeled and diced
4 cups/960 ml water
11/2 tsp granulated sugar
1/2 tsp freshly ground pepper
5 cups/120 g lightly packed chopped radish tops (from 3 bushy bunches)
5 or 6 radishes, trimmed and cut into matchsticks
In a heavy soup pot, melt the butter over medium-low heat and swirl to coat the pot bottom. Add the leek, onion, carrot, and salt and stir briefly. Cover and cook, stirring once or twice, until the vegetables are very soft but not brown, about 20 minutes. Uncover, add the potato, water, sugar, and pepper, increase the heat to medium-high, and bring to a simmer. Adjust the heat to maintain a simmer, re-cover, and cook, stirring occasionally, until the vegetables are tender when pierced with a fork and soft enough to purée, about 35 minutes. Add the radish tops and stir until the greens are wilted, about 1 minute. Remove from the heat and let the soup cool for about 10 minutes.
Working in batches, process the soup to a smooth purée in a blender or food processor. (At this point, the soup can be cooled, covered, and refrigerated for up to 2 days.) Return the puréed soup to the pot and place over medium-low heat. If the soup is too thick, add a little water to achieve a creamy consistency. Heat until steaming hot, stirring occasionally.
To serve, ladle the soup into warmed bowls. Place a little clump of matchstick-cut radishes in the center of each bowl for garnish. Serve immediately.