Cream of Celery Root Soup

Traditional thick, creamy soups like this one use a roux-thickened base of stock or milk (a béchamel) and are flavored by the main ingredient, which can be anything from broccoli to celery root to pumpkin. These soups are economical, easy, and enormously satisfying. Following the method here, you can replace the celery root with cauliflower, potato, parsnip, turnip, or carrot. To make a creamy green vegetable soup, use asparagus, broccoli, or another vegetable and substitute chicken or vege