Skillet Pot Soup

My dear friend, Pam, makes a lovely Colcannon recipe with a little horseradish added for "zip".  See her recipe here:
http://www.food52.com/recipes/14207_colcannon_with_a_little_zip 

This inspired me to turn Colcannon into a soup.  I did some research and found that Colcannon is not just an Irish dish, but also the name of a song sometimes called" The Skillet Pot Song" which starts out this way:

"Did you ever Colcannon made from lovely pickled cream?"

After days of research, I could find only one reference to pickled cream, that being buttermilk or soured cream.  Buttermilk sounded just right for my little "zip".  This one's good warm or chilled.

Makes about 2  1/2 quarts

5 Tbl butter or 4 Tbl butter plus 1 Tbl rendered bacon fat
1 large leek, white part only, sliced lengthwise and then cut crosswise into 1/4 inch moons
4 cups chopped cabbage
2 tsp salt
1 tsp black pepper
4 to 5 cups peeled, diced redskin potatoes (3/4 inch dice) 4 to 5 potatoes
6 cups chicken broth
1 bunch chopped kale (5 to 6 cups) chopped
1 cup buttermilk
1/2 cup half and half

In a Dutch oven or soup pot, melt the fat and add the sliced leeks.  saute them until they soften.  Add the chopped cabbage and continue to saute until the cabbage softens up.
Add the salt, pepper, diced potatoes and chicken broth, bring up to a boil and then simmer until the potatoes are tender, 10 to 15 minutes.  Cool the soup to lukewarm.
While the soup is simmering, steam the chopped kale in a little water until wilted and tender.
Once the soup has cooled, process it in batches in a food processor or blender until pureed.  Return the soup to the pot and stir in the kale, buttermilk and half and half.
At this point re warm the soup (don't boil!) or if you would like it chilled, refrigerate for a few hours before serving.