Roux is a mixture of flour and fat cooked together and used to thicken sauces. Roux is typically made from equal parts of flour and fat by weight. The flour is added to the melted fat or oil on the stove top, blended until smooth, and cooked to the desired level of brownness. A roux can be white, blond (darker), or brown.
Basic flour roux for thickening gumbo or other savory dishes.
In a large bottom pan, (Cast Iron works best) bring you oil up to temperature low-medium heat. You can add a drop or two of water to the oil to test its temp and when the water starts to skitter or boil you know the oil is ready. It’s best if you avoid heavily flavored oils such as olive, grape, coconut and others. The taste of the oil does transfer into the flour.
Start mixing the flour in, in stages, while stirring the oil. A Metal whisk works great for this. As you continue to stir in the flour make sure you scrape all of the surfaces of the pan with the whisk so that none of the flour sticks and burns. The goal is here to "brown" the flour. You want the overall consistency of the flour and oil to be that of a medium weight gravy or cake mix. You can always add a bit more flour if the mix is too runny.
Continue to stir the mix for appx 10-40 min until the roux reaches your desired color. You can pull the roux earlier if you want more of a blond look. If the mixture starts to smoke at any point your heat was too high. If you are lucky it’s not too scorched. However it’s probably best if you just start over with less heat and more patience. Stir stir stir…The roux will go through some stages where it’s frothy, then bubbly and then eventually it settles down into a thick creamy texture.
At this point you have cooked your roux to the desired color. The next step is to remove the pan from the heat and continue to stir for a min or two until the pan is cool enough that the flour is no longer browning in the pan. The Roux can be used immediately in Gumbo or other recipes. Alternately it can be put in a container for storage until a later time. Once put in storage there may be some minor separation of the oil from the flour. This is normal and the oil that separates can simply be set aside for cooking other ingredients or simply disposed of. For best results mix cold roux to hot liquids or hot roux to cold liquids.