This is a very basic recipe for a delicious creamy soup that you can adapt in many different ways. Add coconut milk and cilantro for a more tropical flavor; heavy cream and nutmeg for solid comfort food.
Optional: Cut the leaves off 1-2 leeks and wash them. Reserve the shanks. Boil the leaves in 6 C. water for 1 hour or longer. Add fresh or dried herbs: parsley, thyme, etc., if you like. Strain out the herbs and leek leaves before using the broth.
Trim 1 medium or 2 small leek(s) and cut an X down into the shank. Run the leek under water, separating the layers to wash out any dirt. Thinly slice the leek lengthwise, then cut the slices in 1 inch pieces.
Heat 3 T. olive oil and add the leeks. Saute on low heat until the leeks are soft and beginning to brown. Sprinkle 1 T. cumin powder over the leeks and stir to coat, then add 5 C. of the leek broth (or chicken or vegetarian stock). Bring to a boil, then simmer.
Dice 2 lbs. of sweet potatoes and add to the pot. Peel the zest from 1 medium or 2 small lemons, mince it finely, and add to the pot.
While the soup is cooking, shred cabbage finely to make 2 Cups or more.
When the sweet potatoes are soft, puree the soup in batches in a food processor and return to the pot. Add 3 T. lemon juice and season with salt and cayenne pepper to taste.
Top each bowl of soup with a handful of shredded cabbage drizzle with more lemon juice.