1 tablespoon flour
1 tablespoon unsalted butter
1 1/2 cups chicken broth (or vegetable broth, if desired)
1 tablespoon light brown sugar
1 1/2 cups cooked sweet potatoes
1/4 teaspoon ground ginger
1/8 teaspoon ground cinnamon
1/8 teaspoon ground nutmeg
1 cup milk
Salt and pepper to taste
Sour cream for serving (optional)
In a sauce pan or skillet, over medium-low heat, cook the flour and butter, stirring constantly until roux achieves a light caramel color.
Add the broth and brown sugar, bring to a boil, then lower to a simmer. Stir in the sweet potatoes and spices, bring to a simmer again, and cook for 5 minutes more.
In a blender, carefully puree the soup in batches and return to saucepan. To prevent the hot soup from splattering out of the top of the blender, I keep the lid tilted and cover the top with a dish towel, while pulsing.
Whisk in the milk and reheat soup. Season with salt and pepper; ladle into warm soup bowls and serve with sour cream, if desired.