Carrot, Leek and Mushroom Soup

Here's a light starter soup or maybe one to accompany a sandwich. The carrots, leek and mushrooms give it an earthy quality.

3 Tbl butter
2 cups finely chopped leek (white part only)
12 ounces cremini mushrooms, sliced (or mushrooms of your choice)
4 cups sliced carrots
8 cups unsalted beef stock
1/4 tsp ground thyme
2 tsp salt
1/2 tsp black pepper
1/2 cup dry sherry
chopped parsley for garnish (optional)

In a dutch oven, melt the butter and add the leek and mushrooms.  Saute on medium heat for about 8 minutes.  Add the carrots, beef stock and thyme.  Bring to a boil and simmer for 30 minutes.  Add the salt, pepper and sherry.  Bring back to the boil and simmer for 5 more minutes.  Garnish with chopped parsley if desired.