Butternut Squash Apple Soup

1 yellow onion, chopped
1 rib of celery, chopped
1 carrot, chopped
1 Tbsp butter

1 butternut squash, peeled, seeds removed, chopped
1 tart green apple, peeled, cored, chopped (squash and apple should be at a 3 to 1 ratio)
3 cups chicken broth (or vegetable broth if vegetarian)
Pinches of nutmeg, cinnamon, salt and pepper

Combine butter, onion, celery, and carrot in large saucepan. Cook for 5 minutes. Add squash, apple, and broth. Bring to boil. Simmer for 10 minutes or until squash is soft. Puree. Add spices to taste. Dollop of sour cream if desired.