leek potato soup

1 pound leeks
1 pound fresh spinach, kale, or Swiss chard
6 cups low-sodium or homemade vegetable broth, divided
2 medium Yukon gold potatoes, peeled and chopped
freshly ground black pepper, to taste
1/4 cup soy or rice milk
1 teaspoon dried tarragon
Cut off root ends of leeks and remove 1/3 of the green tops. Cut leeks in half lengthwise and slice very thinly. Place leeks in colander and rinse well under cold water. Thoroughly wash spinach, kale, or Swiss chard and remove stems.
Heat about 2 tablespoons broth in a soup pot over medium heat. Add leeks and cook, stirring until they begin to soften, about 6 to 7 minutes. Add spinach and 2 cups broth. Cook for 1 to 2 minutes. Add potatoes and remaining broth. Season with black pepper and bring to a boil. Reduce heat to low and simmer, uncovered, for 30 to 35 minutes.

Next, purée soup in food processor or use an immersion blender for puréeing. After puréeing, return soup to a medium-low simmer, and add soy or rice milk and tarragon, and simmer a few minutes. Taste, adjust seasonings, and serve.