- 1/4 cup plus 2 tablespoons olive oil
- 1/3 medium baguette, crusts removed, bread cut into 1-inch cubes (about 1 cup)
- 1/2 cup minced onion
- 1/2 pound yellow Finn or red potatoes, peeled and quartered
- 3 1/2 cups vegetable stock, chicken stock or canned low-sodium chicken broth
- 1 pound watercress, tough stems discarded
- 1/2 pound sorrel, stems discarded
- Salt and freshly ground pepper
- Heat 1/4 cup of the oil in a skillet until almost smoking. Add the bread cubes and fry over moderately high heat, stirring, until well browned, about 5 minutes. Transfer to paper towels to drain.
- Heat the remaining 2 tablespoons of oil in a large saucepan. Add the onion and cook over moderate heat, stirring, until softened, about 5 minutes. Add the potatoes and chicken stock and bring to a boil. Reduce the heat to low, cover and simmer until the potatoes are tender, about 15 minutes.
- Stir in the watercress and sorrel, cover and simmer over low heat until the greens are wilted, about 5 minutes. Working in batches, puree the soup in a blender. Return the soup to the saucepan and rewarm over moderately high heat; season with salt and pepper. Ladle the soup into bowls and garnish with the croutons.
Sorrel is a perennial herb with a sour flavor. It is shaped like spinach, but the color of the leaves ranges from pale to dark green. Look for sorrel with bright, crisp leaves. The stems should not be woody. While sorrel is available year-round, its peak season is the spring, when it's at its mildest.