This Cream of Watercress Soup is a great winter soup for a cold day. Better yet, it’s really fast to put together. It can be on the table in 30 minutes. Watercress has a... wonderful, peppery taste and is full of vitamins A, C, and K. Adding the finely diced stalks gives the soup extra flavor. The butter or cannellini beans give it a higher protein content than the usual potatoes, and a creamy texture and taste without dairy. If cooking the beans, add the liquid they were cooked in, and cut back on the stock proportionately. If not vegetarian, try making this soup with chicken stock.
Finely dice the thick stalks of the watercress. Set aside. Break up the leafy greens into leaflets, discarding any remaining thick main stems. Set aside and reserve some for garnish.
Heat the oil in a heavy soup pot over medium-high heat. When it starts to ripple, add the onions, diced watercress stalks and thyme. Fry until the onion starts to soften. Turn the heat down to medium, sprinkle with a little sea salt and cover. Sweat the vegetables for 8 to 10 minutes, stirring from time to time. Don't let them burn or color!
Add the beans and their liquid and stir to mix well with the vegetables. Add the stock if using canned beans. Bring to a boil. Turn the heat down and cook until the beans are heated through and can be easily smashed against the side of the pan with a spoon, about 10 minutes.
Add the watercress leaflets to the soup and cook for 5 minutes, until they wilt. Blend the soup until smooth in a blender or with an immersion blender. Bring back to a simmer, add all the watercress leaves and 2 tablespoons of the chopped parsley, and cook a minute more and taste for seasoning. Serve immediately, sprinkling each bowl with the remaining parsley, watercress leaves and a grind of black pepper.