Corn, Watercress, and Potato Soup

1. Thoroughly rinse and drain dark-green leek tops; transfer to a pot. Remove husks and silks from corn, rinse and drain them, and transfer to pot. Strip corn from cobs and transfer cobs to pot (reserving kernels). Add 8 cups water, 2 teaspoons salt, and whole peppercorns to pot. Bring to a boil, then reduce heat to medium-low and simmer 5 minutes. Strain through a fine-mesh sieve, discarding solids and reserving broth (you should have about 6 cups).

2. Slice white and light-green parts of leeks; submerge in water and agitate with your hands to dislodge any dirt, then thoroughly drain. Wipe pot clean; add oil and heat over medium. Add sliced leeks and garlic. Cook, stirring occasionally, until leeks are very soft but not developing any color (if color begins to develop, reduce heat), about 10 minutes. Add potato, 4 cups reserved broth, and reserved corn kernels to pot. Bring to a boil, then reduce heat to medium-low, cover, and simmer until potato is easily pierced with the tip of a knife, about 15 minutes. Stir in all but a handful of watercress; simmer 2 minutes.

3. Transfer soup to a blender with miso and vinegar; purée until smooth. (Be careful blending the hot liquid: Remove feed cap from blender lid and cover with a kitchen towel to let steam escape, and purée in two batches if necessary.) Season to taste and thin with more broth, if necessary, to reach desired consistency. Serve warm or chilled, topped with blanched corn kernels, remaining watercress, a drizzle of oil, flaky salt, and ground pepper.

Cook's Notes

If you don't have watercress, try another peppery green, like arugula. No cider vinegar? Add a pour of white balsamic or a hard squeeze of citrus. This soup will thicken slightly as it cools; stir in more broth or water to reach the desired consistency.