Ingredients
4 1/2 cups homemade or low-sodium store-bought chicken stock
3 medium leeks (about 12 ounces), white and pale-green parts only, cut into 1/2-inch-thick rounds and rinsed well
1 russet potato (8 ounces), peeled and cut into 1/4-inch-thick rounds
1 garlic clove, thinly sliced
1 bunch watercress, largest stems discarded, remainder coarsely chopped, plus more for garnish (optional)
Coarse salt and freshly ground pepper
Sour cream, for serving
Preparation
Bring stock, leeks, potato, and garlic to a boil in a medium pot. Reduce heat to medium; cook until leeks are tender and potato is soft, about 15 minutes. Add chopped watercress; cook until beginning to soften, about 2 minutes.
Puree the stock and vegetables in a blender until smooth (work in batches, if necessary, to avoid filling blender more than halfway). Season with salt and pepper. Top each serving with sour cream, and garnish with watercress, if desired.
