In a medium sauce pan melt equal parts butter and then the flour.
Whisk the flour and butter together and allow to simmer on low to cook the flour.
1-2 minutes: The lightest (white color) roux will be slightly puffed. It can be used in white sauces like pepper sausage gravy or bechamel sauce. 3 minutes: The light (blond color) roux will be slightly puffed. It can be used in sauces like velouté (chicken stock plus roux). 5-6 minutes: A light brown (peanut butter color) roux is perfect for savory sauces or gravies. 10 minutes: Dark (brown color) roux is great for Creole and Cajun recipes.
Add liquids like chicken of beef stock, milk or wine a little at a time while whisking until smooth after each addition. Add remaining seasonings in recipe and simmer a couple of minutes more.
Video
Notes
TIPS:
The roux is the base thickener for any sauce, gravy or soup. Adding 3-4 cups of stock or other liquid will yield a medium consistency when whisked in. Adapt to your liking of more or less. I prefer thicker, which means less stock and add more as you go. You can't go back once it's thinned, BUT you can make more roux and whisk it in to thicken again.
The longer a roux cooks, the less thickening power it has.
If you want a dark roux for a Cajun or Creole dish use a canola or vegetable oil because it has a higher smoke point than butter and will prevent the mixture from burning.I also use shortening or the incredible “liquid gold” that is bacon fat, extra flavor there!
How to Avoid Lumps
To prevent lumps when adding liquids to a roux, the rule is to always add a cold liquid (milk, chicken stock, wine, etc.) to hot roux.
If using a cold roux straight from the refrigerator, whisk it into hot liquids (chicken, beef or vegetable stocks).