Watercress Soup

Watercress soup can regularly is discovered, while in season, in the herb segment of the grocery save. The bunches need to be thick-stemmed, and the leaves have to have a sturdy, peppery chunk to them. The sensitive, skinny-stemmed toddler watercress that some markets convey isn't appropriate for this soup.


INGREDIENTS
3 tablespoons butter
2 cups white or yellow onion, chopped
Salt
1 cup white wine, chicken stock, or vegetable stock (wine or veg stock for vegetarian version)
1 pound potatoes, peeled and cut into chunks
6 cups of water
6 cups fresh watercress, about 1/2 pound, chopped, stems included
1/2 teaspoon black pepper
About 6 tablespoons sour cream, stirred in, or for garnish

METHOD
1 Cook the onions: In a large pot, heat the butter until frothy, then cook the onions over medium heat until soft and translucent, about 5 minutes. Salt the onions as they cook.

2 Add potatoes, wine/stock, simmer: Add the wine or stock, potatoes, and water and bring to a boil. Turn the heat down to low, cover the pot and simmer until the potatoes are soft, about 30 minutes.

3 Add watercress: Add the watercress to the pot. Stir well and cook for 2 minutes.

4 Purée the soup: Turn off the heat and purée the soup with an immersion blender. If you don't have an immersion blender, pour the soup in batches into a blender and transfer the blended soup to a clean pot. Be careful when blending hot liquids to only fill the bowl a third of the way, and to hold down the blender's lid while you purée the soup.

5 Season and garnish to serve: Add salt to taste, then add the black pepper. You can either stir the sour cream into the whole batch of soup or serve a tablespoon in the center of each person's bowl.