Roux: The Secret Behind Some Great Sauces

Do you know what a roux (pronounced “roo”) is? Think of roux as a thickener for sauces, gravies, stews, and soups. It combines equal parts flour and butter. It’s one of those foundational things that you really should know - and will turn to on a regular basis. Another reason to know how to make a roux is that it’s used as the foundation for three of the five “mother sauces” of classical French cooking: béchamel sauce, velouté sauce, and espagnole sauce. (What?!?!? You’re not familiar with those five “mother sauces”? You can read about them here: "Can You Make the Five 'Mother Sauces'?".) So, think of it as a fundamental element of making sauces.

Butter is used most often, but different fats can certainly be used. And different cooking traditions outside French cooking may use fats such as vegetable oil, clarified butter, lard, or duck fat.

If you are making a roux for future use, consider using clarified butter as the fat. It will harden when it’s refrigerated and the flour will be suspended in it (a good thing). That suspension helps to prevent lumps when the roux is whisked into a sauce or soup later. 

I know flour has kind of a raw taste, but using it in a roux cooks out that raw flavor and what you are left with is a silky-smooth, slightly nutty foundation that can be used to make sauces and other recipes (like mac-and-cheese)

How to Make It

Making a roux is a pretty easy thing. Just follow these three easy steps and you're there:

  • Step 1: Begin by heating the fat usually butter) until it’s melted.
  • Step 2: Once the butter is melted, add the flour and stir until smooth. What you are doing is coating the flour with fat which prevents it from forming lumps when mixed with a liquid later.
  • Step 3: Cook it over medium-low heat and stir constantly to prevent scorching. (NOTE: Be careful that your heat is not too high. It will burn the roux, and make it grainy and poor tasting).

White, Blond, and Brown

How long you cook the roux depends on what you will be using it for. Beyond that, how long you cook the roux depends on what you're using it for. A béchamel sauce calls for a “white” roux, so you'll only want to cook it for a few minutes, until the raw flour taste is gone but the roux is still a pale yellow.

White roux

White roux

A “blond” roux, used in white velouté sauces, needs to be a bit darker, so it's cooked a minute or two longer.

A “brown” roux, used in brown sauces, is the darkest roux. It is cooked for the longest amount of time. So cook it over a lower heat so that you don't burn it. Some cooks even brown the flour in the oven before adding it to the butter. Note: The roux's thickening properties are reduced as it gets darker.

Using Your Roux

Since roux is a base for other recipes, you typically mix other ingredients/liquids into it (instead of mixing the roux into the liquid). One hint is to warm those liquids a little before gradually adding them to the roux (whisking them together constantly). If the liquid is too cold it will take longer to bring together. On the other hand, if it’s too hot your sauce will  thicken too quickly resulting in a lumpy sauce. After you bring the mixture together, just allow it to simmer gently.

As a general rule-of-thumb sauce made with a roux should simmer for at least 30 minutes. The liquid reduces and thickens, the pasty taste of raw flour disappears completely, and the sauce becomes rich tasting and velvety smooth. Perfect!

Let’s be just a little more precise here. The “equal” parts flour and fat - it’s better to do those measures by weight (using a digital scale), not volume. It’s more accurate - especially because they are two kinds of substances. A given weight of butter will absorb an equal weight of flour. Clarified butter is pure butterfat, so you can use equal amounts of each. If you’re using whole butter (which is fine too), on the other hand, use just a little less flour. Since whole butter is really 15% water it will evaporate off and once it does the levels of flour and fat will be equalized if you use a little less flour to start.

What's Really Going On?

Some people (me included!) like to know why things work as they do. For you, here’s a quick lesson on why and how a roux works to thicken a liquid. What’s happening is that the starch molecules in the flour absorb the liquid and expand, becoming slightly gelatinous. This is what is thickening the sauce.  And the fat helps keep the starch molecules separate, so that they don't clump up and form lumps. 

Storing Your Precious Roux

Brown roux

Brown roux

If you are not using all of your roux right away it can certainly be stored. I mentioned above the secret to successfully refrigerating the roux. And it can be stored in the fridge almost indefinitely without any problem. If you want to store it for the longer-term and free up your refrigerator space, consider freezing it. Just pour some in ice-cube trays or muffin tins so you’ll have smaller amounts that can be used when needed. Just pull them out and bring them to room temperature when needed. Easy!

So, my home-cooking friends, it's time to master roux. It's easy and it can be used frequently. Having a well-made roux on hand will make it easy to use this marvelous thickener in everyday cooking.

If you liked this post, you may also want to check these out:
- Master a Great Pan Sauce
- Let's Talk Brown Butter
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