Generally for a roux: to thicken 1 cup (8 oz / 250 ml) of liquid such as milk or broth you need:
  1. Thin sauce: 1 tablespoon of flour / 1 tablespoon of butter.
  2. Medium sauce: 2 tablespoons of flour / 2 tablespoons of butter.
  3. Thick sauce: 3 tablespoons of flour / 3 tablespoons of butter


Choose a fat to use.

A roux is another French word that describes the paste created by cooking fat with equal parts flour. The recommended fats are oil, butter, extra virgin olive oil, or drippings. A roux can be used to thicken gravies, savory sauces, stews, or soups.


  1. Place fat into a sauce pan over medium heat. Depending on how thick you want your sauce, use between one and three tablespoons of fat plus equal amounts of flour per cup of liquid. 
  2.  For a basic  roux  cook the flour and fat together for a few minutes, until they are fully incorporated.
  3. Whisk the roux (it can be used cold, warm, or hot) into the sauce/soup- bring to a simmer and cook for at least 10 minutes to cook off any remaining flour taste.


Cornstarch is the most common starch used for thickening, but you can also use potato starch, arrowroot flour, tapioca flour, or rice flour. When combined with liquids and heated, these starches swell and form a thickening gel.

A general rule of thumb to substitute cornstarch for flour: 2 tablespoons wheat flour = 1 tablespoon cornstarch. For a medium consistency sauce, add 1 TBSP Cornstarch mixed with 1 TBSP of water or milk.

Whisk in equal parts cold water. For every tablespoon of starch you added, add one tablespoon of cold water to the starch. Whisk until there are no lumps and the starch is fully incorporated.

Whisk the slurry into your sauce. Pour the starch slurry slowly into the sauce you want to thicken, whisking constantly to incorporate the slurry into the sauce.

After you add the slurry, cook the sauce for about 4 or 5 minutes so that the starch granules completely gelatinize.

Bring to a simmer. To release the starch molecules, you must heat the sauce to a simmer, otherwise the starch won’t thicken.

Reducing Liquids

Bring your sauce to a simmer. .This method works well with most sauces, because as a sauce heats up, the water will evaporate, leaving a thicker and more concentrated sauce behind.


Powdered, unflavored gelatin is tasteless and virtually colorless and derived from animal collagen. It can be used as a thickening agent for savory sauces, like a demi-glace, or in a sweet berry sauce. Gelatin  thickens as it cools, in contrast to starch thickeners, like flour or cornstarch, which thicken when heated.

In fact, just about any recipe that calls for canned broth will likely benefit from the addition of gelatin. About 2 teaspoons of gelatin per cup of broth thickens sauces and braises appropriately, and adds a rich mouth feel.


Here’s how to incorporate it:

Step 1

Add about 2 tablespoons of cold water to a small bowl. Measure out the powdered gelatin. Use 2 teaspoons of gelatin for every 1 cup of sauce liquid for thin sauce, and up to 4 1/2 teaspoons of gelatin per 1 cup for thick sauce. Sprinkle the powdered gelatin over the surface of the water.

Step 2

Whisk the gelatin and water together. Allow the gelatin and water mixture to sit for a few minutes to hydrate the gelatin powder.

Step 3

Pour the mixture into a simmering pot sauce. Stir the sauce for about one minute to integrate the gelatin with the sauce. Do not allow the sauce to boil after you’ve added the gelatin.

Step 4

Remove the pot of sauce from heat. Allow the sauce to cool at room temperature until it begins to thicken slightly, then serve warm.


Using gelatin to set cold liquid.

  • One tablespoon of gelatin will set two cups of liquid when chilled.
  • One package of powdered gelatin is roughly equal to one tablespoon.
  • Four sheets of gelatin equals one tablespoon of powdered gelatin.
  • If a recipe says to “bloom” the gelatin, that means to hydrate it in a small amount of water.
Michael holding plate of pesto crab cakes

Hello, I'm Michael!

I aspire to share recipes that you and your family can enjoy while also learning about cooking fundamentals along the way. I attended the California Culinary Academy in San Francisco, CA and now enjoy cooking as a hobby. 

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