How to Thicken Soups and Sauces (6 Ways)

Pick the right method

Thickeners aren't interchangeable. Some add flavor, some add richness, some keep a sauce glossy and clear, and some don't survive freezing. Start with what you're making and when you noticed it was thin.

Roux (the start-of-the-recipe thickener)

Cook equal parts butter and flour over medium heat for 2 to 3 minutes, until it smells like popcorn, then whisk in the liquid a little at a time and simmer. That's how loaded baked potato soup, broccoli cheddar soup and new england clam chowder get their body. For a soup, use about 1 tablespoon each of fat and flour per cup of liquid; for a gravy or sauce, about 2. It has to come to a full simmer to thicken all the way. For colors, ratios and dark roux, see the full roux guide.

Cornstarch slurry (the fast fix)

Stir 1 tablespoon of cornstarch into 2 tablespoons of cold water or stock until smooth. That thickens about 2 cups of liquid to a light sauce. Pour it into the simmering pot while stirring, and keep stirring as it comes back to a gentle bubble. It turns from cloudy to clear and thickens in about a minute.

Don't keep it at a hard boil or stir it hard for a long time; cornstarch breaks down and the sauce thins out again. It also turns spongy when frozen, so for soups headed to the freezer, use flour or a purée instead.

Swaps: Arrowroot or potato starch work the same way and stay clear and glossy, but break down even faster with heat, so add them at the very end. Use 2 tablespoons of flour in place of 1 of cornstarch, and simmer a few minutes longer.

Reduction (the no-extra-ingredient way)

Simmer the liquid uncovered over medium-high heat. As water steams off, the flavor concentrates and the texture thickens, especially in anything with gelatin from bones or meat. Use your widest pan; more surface means faster. A cup of pan sauce reduces by half in 5 to 10 minutes.

Taste before you add salt. Reducing concentrates everything, including the salt already in the stock.

Purée, potatoes and other pantry tricks

• Purée part of the pot. Blend a third to half of a bean, vegetable or potato soup and stir it back in. It stays chunky but turns creamy. Use an immersion blender in the pot, or fill a regular blender no more than half full, remove the center cap and cover the hole with a folded towel so steam can escape.
• Mash in the pot. For loaded baked potato soup, corn chowder with bacon and bean soups, a few strokes of a potato masher thicken things right away.
• Add a starchy potato. Peel and dice a russet and simmer it in the soup until it falls apart, then mash or blend. Leftover mashed potatoes or a spoonful of instant potato flakes do the same in a minute.
• Rice, small pasta or oats. A handful simmered in the soup releases starch. Serve right away; they keep soaking up liquid.
• Stale bread. Torn and simmered in tomato or vegetable soup, it melts into a thick, rustic texture.

Beurre manié, egg yolks and cream (the rich finishes)

Beurre manié is French for "kneaded butter." Mash equal amounts of soft butter and flour into a paste, about 1 tablespoon of each per cup of liquid. Whisk in a small lump at a time to a simmering stew or gravy and let it bubble for 3 to 5 minutes after each addition. The butter keeps the flour from clumping, so it's an easy fix when a beef stew with chuck and red wine or chicken and dumplings with buttermilk drop dumplings comes out thinner than you wanted. Make extra and keep it in the fridge for a week.

Egg yolks give a creamy soup a silky body. Whisk 2 yolks in a bowl, then slowly whisk in roughly 1 cup of hot soup to warm them. Stir that back into the pot over low heat and heat gently, without boiling, until it coats a spoon and reaches 160°F.

Heavy cream thickens a sauce as it reduces, and won't curdle at a simmer. Half-and-half and milk curdle more easily, and sour cream and yogurt curdle quickly, so stir those in off the heat. A few cubes of cold butter swirled into a pan sauce at the end add body and shine.

Common mistakes

• Dumping dry flour or cornstarch into hot liquid. It forms lumps instantly. Always mix starch into cold liquid first, or into fat as a roux or beurre manié.
• Judging the thickness too early. Starches reach full thickness only at a simmer, and soups thicken more as they cool. Give it a few minutes of bubbling before adding more.
• Adding it all at once. Add half, simmer, look, then add more. A soup that's too thick is easy to thin; a gluey one is hard to love.
• Boiling a sauce thickened with yolks, yogurt or sour cream. It will curdle. Keep it below a simmer.
• Salting before reducing. Wait until the end so it doesn't get too salty.
• Using cornstarch for a soup you'll freeze. It goes thin and spongy when thawed. Use a roux or purée.

Too thick instead?

Thin it with warm stock, milk or water, a splash at a time, and bring it back to a simmer. Soups made with roux, potatoes or beans thicken in the fridge overnight, so plan on adding a little liquid when you reheat leftovers. Taste for salt again afterward.