Creamy Turnip and Carrot Soup

This is a basic recipe that can have anything else you have on hand added to it if you like.  My most recent version used purple carrots (which turned the whole soup purple!) and I added garlic and celeriac to it, also.  I love this kind of soup because it's so adaptable!

2 tablespoons butter or oil
1 medium onion, or two large shallots
3 cups turnips, peeled and chopped
2 cups carrots, peeled and chopped
4+ cups chicken broth or vegetable broth
salt and pepper to taste
1/2 cup to 1 cup cream or milk

Over medium heat, saute onion gently in oil until translucent, about 3-5 minutes.  Add turnips, carrots, and broth.  Bring to boil and simmer until veggies are tender, about 20 minutes.  Puree and then add cream and season with salt and pepper to taste.