Sweet Potato Leek Soup

This is a sweet and creamy variation on the more traditional potato leek soup, inspired by the sweet potatoes and leeks in our CSA share. Whole wheat popovers made a nice accompaniment.

1 Tbsp butter
3 fat leeks, sliced
2 lbs sweet potatoes, peeled and cubed
3 medium potatoes (about 1 lb), peeled and cubed (smaller than sweet potatoes)
Water or chicken/vegetable stock
2 tsp cider vinegar
1 cup milk (optional)
1/2 - 1 tsp paprika
Salt and pepper to taste

Melt the butter in a large pot, then add the leeks and saute for 3-4 minutes. Add the sweet potatoes and potatoes and enough water and/or stock to just cover them. Bring to a boil and cook until tender, about 15 minutes.

When the sweet potatoes and potatoes are tender, puree the soup using an immersion blender (or do it in batches in a blender or food processor). Stir in the cider vinegar, milk if using, paprika, and salt and pepper. Taste and adjust seasonings.

Serve hot. Serves 4-6.

Variations:
1. Omit the paprika and season to taste with sage or rosemary.
2. Add one or more minced chipotle peppers in adobo sauce.
3. Add 1/2 lb cooked crumbled Italian sausage (sweet or hot)
4. Add silken tofu before blending, for some additional protein