A roux (?rü) is a combination of equal parts by weight of flour and fat (Butter, oils, drippings, etc). The flour and fat are then cooked together and form a paste.
A roux is considered a staple of most kitchens, and is used as a binder/thickener in countless recipes. At many of the restaurants that I worked in, we would make a large batch of roux in the morning, and use it as the cooking day progressed.
Roux Blanc (white): The flour and fat are cooked for a very short time. It should be removed as soon as it begins to simmer.
Roux Blond (blond): The flour and fat are cooked for a longer period of time, and begin to take on some color. A Roux Blond is at the beginning stages of becoming caramelized.
Roux Brun (brown): The flour and fat are cooked for an even longer period of time, until the mixture darkens even more, and begins to take on a nutty aroma. In French cooking a Roux Brun is typically not made with butter, but with drippings.
The Roux Brun is much more caramelized, and will develop a distinct brown coloring.
THE THICKENING POWER OF A ROUX
There are many variables to how much a roux will thicken a liquid. For example, you have the content of the flour (higher protein flours thicken less), plus other ingredients (salt, sugar, etc); even the age of the flour can influence its thickening ability. With all things considered, let’s assume that you are using fresh all-purpose flour (not self rising), and you are using an equal amount of clarified butter.
The following example is the amount of Roux Blanc you would need when thickening one cup of liquid:
• Thin Sauce: 1 tablespoon of flour and 1 tablespoon of fat.
• Medium Sauce: 2 tablespoons of flour and 2 tablespoons of fat.
• Thick Sauce: 3 tablespoons of flour and 3 tablespoons of fat.
There are so many variables it is hard to quantify the actual results you will get, and this this is why most cooks rely on a little experience and a lot of observation.
Chef’s Note: Many chefs prefer to use cake or pasty flour to make a roux, because of its higher starch content.
MEASURING THE INGREDIENTS OF A ROUX
Most recipes for a roux suggest equal amounts, by weight, of flour to fat. For example, if you were using 50g of flour, you would need 50g of fat… no rocket science there. However, unless you are making a ton of roux (that’s a lot), measurement by volume is perfectly acceptable. We’ll be using US measuring spoons for this lesson, primarily the tablespoon. For a metric conversion, a US tablespoon is equal to 14.7ml.
COOKING TIMES FOR A ROUX
The longer you cook a roux, the less power it has to thicken your sauce.
• Thin sauce: 1 tablespoon roux to cup of liquid.
• Medium sauce 2 tablespoons roux to cup of liquid.
• Thick sauce: 3 tablespoons roux to cup of liquid.
• Thin sauce: 1.25 tablespoons roux to cup of liquid.
* Medium sauce: 2.5 tablespoons roux to cup of liquid.
• Thick sauce: 4 tablespoons roux to liquid.
A dark brown roux has very little thickening power; mostly they are used for flavor more than actual thickening. However, you would need to double the amount of roux, to achieve any thickening power.
Clarified butter will improve the roux's thickening power and it combines more easily with the flour, than regular butter.
In addition, regular butter contains water and milk solids (up to 15 percent), when using regular butter, you need to add an additional 15 percent of butter to the flour, and then wait until the foaming stops; which means the water has evaporated.
If you are using butter, always try to use clarified butter; it will give a cleaner taste to the roux.
WHY NOT ADD THE FLOUR DIRECTLY TO THE SAUCE OR SOUP
The butter or oil in the roux basically serves to keep the starch grains separate. If you simply added raw flour to the liquid, it would cause the flour to clump and you would wind up with lumps in your sauce. I HATE it when that happens.
In addition, a good reason to cook a roux is that raw flour gives a flour taste to your sauce or soup; however, cooking it helps to eliminate that flour taste.
MAKING THE ROUX
Use a good heavy-bottom saucepan over medium heat, as this will help to evenly distribute the heat, and prevent the roux from burning.
Add the fat (butter/oil) to the pan. If you are using regular butter wait for the butter to melt and the foaming to subside
Add the flour and whisk the flour and fat into a paste.
Continue to whisk until the desired roux is achieved.
THE PROPER WAY TO ADD THE ROUX TO THE RECIPE
You can add cool, or warm, stock to a hot roux.
You can add a room-temperature roux to a hot stock.
You cannot add a hot roux to a hot stock… The high temperature will begin cooking the roux, and you will wind up with lumps.
In all cases, you will be whisking vigorously while adding the roux.
Chef’s Note: My favorite method is to add a bit of cool stock to the roux and whisk to get things started. Once they have nicely incorporated, I add it to the rest of the stock.
Chef’s Tip: Avoid using aluminum pans to make a roux. The combination of the metal whisk against the side of the pan will impart a metallic taste to the roux.
Chef's Tip: Making a roux butter. Take a pound of softened clarified butter and a pound of flour. Mix them together and then wrap in cling foil. Now, when you need a roux, slice off a piece, throw it into a saucepan, and there you go.