Slice leeks in half. Soak in cold water for 5 minutes. Clean thoroughly by swishing in the water and then under running water, separating the leaves to clean all of the trapped dirt. Chop the leeks and place them in a large soup pot.
Clean the green onions. Cut off the tough green ends (just the very tips). Slice the greens and white parts of the onions and add them to the soup pot.
Add the cleaned, chopped celery to the pot.
Pour the vegetable broth over the vegetables and turn on the heat to medium-high. Bring to a boil and turn the heat down to low.
Add the chopped mushrooms.
Clean and chop the Swiss chard. Start by cutting off the stalks. Trim the ends and chop. Add the chopped stalks to the soup. Cut the Swiss chard leaves into bite-sized pieces and add them to the soup.
Chop the spinach and add to the soup.
Cook for about 10 minutes until the vegetables are tender.
If using the cannellini beans and/or potatoes, add to the soup.
Stir in the bouillon paste, tarragon, and black pepper to taste.
Bring back to a boil and cook for 5 minutes.
If you don’t have access to Swiss chard, you can add other greens, such as kale, collard greens, and parsley. Kale and collards take a bit longer to cook than chard. You can also add fresh herb. Try adding cilantro, thyme, oregano, or other herbs of choice to end of the cooking time.
If you are making this soup for a first course, consider serving it with another Spring recipe, Spring Pasta with Zucchini and Watercress.
For a Spring dessert, try our Rhubarb and Strawberry Pie.
If you are serving it as a main dish with potatoes and/or beans, consider teaming it with our Middle Eastern Beet Salad.