How to Thicken a Sauce or Soup

Difficulty level: Easy

Sometimes you can boil a sauce or soup long enough to obtain the perfect thickness, but that’s not necessarily efficient or nutritious, so here are some easy ways to thicken without cooking for an extra hour.

Make a roux

For some reason, the thought of making a roux strikes fear into some cooks’ hearts the same way soufflé does, but making a roux is actually very simple, especially for small amounts. All you need is some kind of fat (such as butter or olive oil) and an equal weight of all purpose flour. As for how much of each ingredient, it depends on the type and amount of liquid you’re trying to thicken:

  • To thicken 2 cups of sauce, use 1 oz fat + 1 oz flour
  • To thicken 4 cups of sauce, use 2 oz fat + 2 oz flour
  • To thicken 2 cups of soup, use 1½ oz fat + 1½ oz flour
  • To thicken 4 cups of soup, use 3 oz fat + 3 oz flour

If you find that the consistency is still not right, make a bit more roux next time.

As for how to make the roux, it’s very simple:

  1. Over medium heat, melt the butter or heat the oil until just warm.
  2. Slowly sprinkle in the flour, whisking constantly.
  3. Continue cooking and whisking the thick paste that forms for 2-3 minutes, until pale yellow. This is called “white roux” and can be used for béchamel and other milk- and cream-based sauces and soups.

At this point, you can either make the sauce or soup right in the same pan (slowly start adding liquid, stirring constantly, and complete the recipe as usual), or you can use this roux to thicken a soup or sauce you’ve already made. To do this, slowly pour some of the warm soup or sauce into the roux, whisking constantly, until completely incorporated, then add the mixture back into the pot, stir well, and let simmer for about 5 minutes, until hot and thick.

The trick to roux is to make sure to add the liquid slowly and get all of the lumps out before you add it into the main recipe. It’s a lot easier to find lumps and get rid of them in a few ounces than in a few cups!

Other ways to thicken

To thicken small amounts (a cup or so) of soup or sauce, you don’t even need to make a roux.

Flour: put 2 t flour in a bowl with with a few ounces of whatever you’re making, mix well, and then add back into the soup or sauce. Simmer until thickened.

Arrowroot or corn starch: Place a T in a bowl with a T of cold water or other liquid, mix well, and add to the soup or sauce. Simmer until thickened.

Cashew butter: only if a slight sweetness is acceptable. Transfer a bit of the soup or sauce to a bowl, stir in a T or two cashew butter until it dissolves, then transfer this mixture back into the soup/sauce. Heat another few minutes, stirring frequently.

Sauce Recipes

Soup Recipes