Step 1

Melt the butter in a saucepan over medium heat. Begin by melting 1 tbsp (15 grams) of butter in a small saucepan. You will know the butter is heated when you can sprinkle a pinch of flour over it and the mixture slowly starts to bubble.You can substitute oil for the butter to make it a dairy-free option.

Step 2

Whisk 1 tbsp (9 grams) of flour into the butter until a thick paste forms. Keep the mixture over medium heat. Whisk it constantly while the flour begins to bubble. As the flour and butter cook, they will become smooth and start to thin.

Step 3

Stir the mixture while you cook it for 5 minutes. Roux does not take long to prepare. It is done when the flour loses its raw smell, and it becomes a thin, white paste.Use roux to thicken milk-based sauces, such as cheese sauce for macaroni and cheese.You can let the roux cook longer to get a blond, brown, or dark brown roux, but these are commonly used to thicken soups and chowders, not sauces.

Step 4

Add room temperature roux to your hot liquid. Whisk the mixture vigorously. Cool your hot roux in the fridge or let it sit out on the counter until it reaches room temperature.Hot roux can be added to cold or warm sauces right away.Do not add hot roux to a hot liquid, as it will create lumps that can not be removed unless you use a strainer.

Step 5

Boil the sauce 1 minute on high. Turn the stove heat up to high and allow your sauce to come to a boil. The mixture will only take about 1 minute to begin thickening. Keep your sauce at a boil until it has reached your desired thickness.

Step 6

Pour any leftover roux onto a baking sheet or ice cube tray. Place your roux in the refrigerator to let it cool overnight or until it has hardened.Keep any leftover roux in an airtight container and freeze it or refrigerate it for up to a month.Roux made with oil can be stored at room temperature for 2-4 weeks.