Creamy Potato Leek Soup

from Moosewood Restaurant's Low-Fat Cookbook

1 cup finely chopped onions
2/3 cup finely chopped leeks
1/2 tsp salt
1 tbsp vegetable oil
4 cups vegetable stock
4 cups coarsely chopped potatoes
1/4 tsp ground fennel
1/2 cup finely chopped celery
2 tbsp white wine
1/2 tsp dried dill
2 tsp dijon mustard
2 tbsp minced scallions
1 1/2 tbsp minced fresh basil
1/2 cup evaporated skimmed milk
4 cups loosely packed shredded kale
salt and ground pepper to taste
squeeze of fresh lemon juice (optional)

1. In a 3 or 4 quart covered soup pot, saute onions, leeks, and salt in the oil on very low heat for about 7 minutes until tender. Add the stock and bring it to a boil. Add the potatoes, fennel, celery, wine and dill. Simmer for about 20 minutes, covered, until potatoes are tender.
2. In a blender or food processor, puree the soup in batches until smooth. Return the soup to the pot and stir in the mustard, scallions, basil and evaporated skimmed milk.
3. In a seperate pot, gently boil the kale in just enough water to cover, When the kale is just tender, drain it and stir into the soup. Add salt and pepper to taste and lemon juice, if desired. Carefully reheat the soup until it is very hot but not boiling.