There are several ways to thicken soups a little or a lot, depending on what consistency you're going for. Here are popular techniques and tips for getting the results you want.
Pictured: Butternut and Apple Harvest Soup
Ways to Thicken Soups
Roux, which is equal parts fat and flour, is common as a thickener because it not only thickens, but stabilizes, too. If cream or cheese is being added to a soup, a bit of roux can insure it won't "break," or separate. Get step-by-step directions for making roux.
Add cornstard to a small amount of cold water or other liquid (wine or stock) and whisk into a thick slurry. This slurry is stirred a bit at a time into the simmering soup at the end to set the final consistency of the soup. Just remember, after you add some of the slurry, let the soup return to a simmer—cornstarch is a very effective thickener, and a little bit can go a long way.
Potatoes, Rice, and Bread
Cooked potatoes or rice can be mashed or puréed and added to soup for more body. Simmering potatoes and grains in soup will also thicken the liquid slightly. Bread crumbs are used to thicken Italian Wedding Soup.
Stir full-fat cream into warm, not boiling, soup to add richness and body after the soup is fully cooked. Full-fat milk and sour cream can also thicken soup, but be sure not to boil the soup after adding the dairy to prevent the soup from curdling.
The Soup Itself
A great trick to thickening a soup while intensifying flavor is to use parts of the soup itself as the thickener. Simply remove some of the soup solids—the aromatics, starches, even the meat—and puree. Use a countertop blender, food processor, or immersion blender for this task. Puree with care if using a countertop blender—the hot soup solids can actually spin out of the blender and make a big mess or cause burns. For best results, fill the blender no more than halfway (blend in batches if necessary). Hold down the blender lid with a thick towel while blending, and keep the lid on for several seconds after the blender is turned off.
Bonus: Here's a hot tip for a soup thickener you've probably never thought of. So genius.