Roux has more complex reactions going on behind the scenes than it appears. You have a fat coating each starch granule, which allows them to gelatinize and dissolve while preventing them from stretching into strands -- which happens when you add raw flour by itself to a soup or sauce. On top of that, roux lends its own special flavor to sauces and soups, which you can't get with pure starches. Unlike pure starches, though, you have to cook the starch out of a soup or sauce thickened with roux, which tastes like raw starch granules on top of the palate.
Things You'll Need
- Cool stock or broth
Cook 2 tablespoons of roux to the desired color -- white, blond, brown or dark -- for every cup of liquid in a pan over medium heat while stirring frequently to keep it from burning. In general, the roux color should match the final color of the sauce or soup it's thickening. The darker a roux gets, however, the less thickening power it has.
Cook the roux an additional two minutes after it reaches the desired color while stirring constantly to cook out much of the floury taste. Add room-temperature stock or broth to the roux.
Adjust the heat to medium-high and bring the stock or broth to just a bit above simmering, or about 200 degrees Fahrenheit. Roux reaches its maximum thickening capability at 200 F, but the sauce or soup gets thicker by reduction when you cook the flour out.
Whisk the soup or sauce several times after you add the stock or broth and while it simmers.
Simmer the soup or stock until it doesn't feel like the top of your palate is coated with starch granules when you taste it. The amount of time varies with the amount of roux, but about 15 minutes usually does it.
Taste the sauce after the flour taste cooks out and determine whether it needs to be thickened more. If so, continue simmering until it gets to where you want it. Season the soup or sauce to taste a final time after it reaches the desired thickness.
Tips & Warnings
- If you're using precooked roux, heat the stock or broth before you add the roux.
- Don't add stock or broth straight from the refrigerator to a hot roux, or it will briefly harden. Let the stock or broth come to room temperature first.
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