Starch Thickened Sauces

a Roux, Beurre Manié, and a slurry. Rouxs are the most common as they are very easy to master, their results are consistent and they can help bring more flavor to your dish.

A roux is equal parts (by weight) of flour and butter. For every quart of liquid, you need 3 ounces of roux. In other words, 1 ½ ounces flour (about ⅓ cup) and 1 ½ ounces butter (3 Tablespoons).

To prepare a roux, heat the butter in a medium saucepan or saucier over medium-high heat until the water has evaporated out but the milk solids haven’t browned. You will know you’ve reached this stage when the butter has stopped foaming and no new bubbles are forming. At this point you can add your flour and whisk until the mixture is a golden blonde color.

For more flavor, albeit less thickening power, you can continue cooking the roux until it is a rich brown color. If you want to compensate for loss of thickening power you can add an additional tablespoon of flour for every quart of liquid you are thickening for a brown roux.
If done at a lower temperature you can go beyond this stage to get a chocolatey dark brown color. This process cannot be rushed with higher temperatures. Doing so will result in a burnt tasting end product. These darker roux compliment the flavors of richer sauces and stews.

A completed sauce or soup that has not reached the desired thickness can be corrected with a beurre manié which means kneaded butter. It is basically an uncooked roux with the exact same ratio and thickening power. To prepare, mix equal parts of room temperature butter and flour together, kneading it until homogeneous. Then, simply roll pea sized balls and chill. It is a good idea to keep a handfuls worth in the freezer for long-term storage so you always have some ready in a pinch.

When using them to correct a sauce, only add a few balls at a time to your simmering liquid. Be sure to make sure they are fully incorporated and to allow the sauce to simmer for a few minutes to thicken before adding any more. It is easier to correct an under-thickened sauce than an over-thickened one.

The final starch-thickened sauce technique is the use of a slurry. A slurry is a mixture of cornstarch and water. One ounce of cornstarch can thicken 1 quart of liquid. You can either blend the cornstarch into your liquid and bring it to a simmer, or, you can add it to an already simmering sauce. To do so, put your cornstarch into a small, sealable container with just enough water to make a runny mixture (traditionally twice the amount of cornstarch by weight). This is most easily achieved by shaking, not stirring. Then you can drizzle the slurry into your simmering liquid while whisking.