In a heavy saucepot, 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, puree the soup in batches and return to saucepot. Add the milk, and reheat soup. Season with salt and pepper, ladle into warm soup bowls and serve.
Recipe courtesy of Cooking Live