Pre-made roux is the easiest way to thicken soups and sauces.

Making a roux takes time, between 10 and 30 minutes depending on the desired color. It's a simple mixture of flour and fat that serves a dual purpose: thickening and adding flavor and texture to soups, stews, and sauces. A white roux is ready in about five minutes, ideal for macaroni and cheese or a New England-style clam chowder, while a darker one can need up to half an hour of simmering.

When preparing a large quantity, it's best to make the most versatile version, the blond roux. At this stage, it retains its thickening power and a mild nutty flavor, and it's the base for three of the five mother sauces: béchamel, velouté, and espagnole. Once cooled to room temperature, freeze it for an hour in an ice cube tray and then transfer it to a resealable bag or airtight container. It will keep for six months to a year this way.

When it's time to prepare the sauce, simply add the frozen cubes to the simmering liquid and cook until you reach the desired consistency, without any lumps. If you want a darker roux, cook it to the desired color before freezing.

The color of the roux also determines the fat used. White and blond roux can be made with butter, but for a darker shade, it's best to use clarified butter, ghee, or vegetable oil, because the milk solids burn and require starting over. A burnt roux is beyond repair. A roux made with vegetable oil will keep for several weeks at room temperature without refrigeration.