Creamy Butternut Squash Soup

2 pounds butternut squash, peeled and cut into chunks
4 cups Rich Chicken Stock or other stock
1 1/4 cups sour cream, creme fraiche or heavy cream
2 tablespoons butter
salt and freshly ground black pepper
teaspoons butter
1/4 teaspoon cayenne, or to taste
about 1 tablespoon sugar (optional)
sauteed or grilled shrimp or mushrooms, optional
several chives, cut into 1-inch pieces

1. Combine the squash and stock in a saucepan and bring to a boil over high heat. Reduce the heat to medium and simmer for about 20 minutes, or until the squash is very tender.

2. Cool a bit for safety�s sake, then puree the mixture in a blender. (You may prepare the recipe in advance up to this point; refrigerate in a covered container for up to 2 days.)

3. Return the puree to the saucepan and turn the heat to medium-low. Stir in the sour cream, creme fraiche, or cream, along with the butter, salt and pepper to taste, and the cayenne. Cook, stirring, until heated through (do not boil), then taste and add sugar and more seasoning, if necessary. Keep warm over low heat.

4. Serve the soup with a few cooked shrimp or mushrooms if you like, and chives.