How Pureed Soups are Thickened

While some starchy vegetables—beans, potatoes, corn, even garlic—act as their own thickeners, some vegetables don’t have enough natural starch to give a soup the desired body and consistency, so an additional thickener is needed.

Flour, gently cooked with vegetables in butter or fat, is one of the most common thickeners. Usually I try to use the vegetable as its own thickener, because flour doesn’t add any flavor and can give the soup a gluey consistency like the clam chowder in cheap restaurants. But flour is very convenient—you can sprinkle a little into the vegetables to give the soup extra body without anyone knowing it’s there. If your finished soup is too thin, you can whisk flour in at the end by working it to a paste with an equal amount of butter and then whisking it into the simmering soup.