Carrot and Parsnip Soup

2-4 tablespoons butter
1 large onion, chopped
1 pound carrots, chopped
1 pound parsnips, peeled and chopped
2-4 cups chicken or vegetable broth
salt and pepper
¼ cup cream or milk

Heat butter in pot on medium.  Add onion and sauté until softened, about 5 minutes.  Add carrots and parsnips, broth, and simmer until tender, about 20 minutes.  Remove from heat and puree.  If too thick, add more broth.  Add salt and pepper.  Add cream or milk.  This soup is also good cold.