1:1 ratio of fat to flour, that’s the basic start to a classic roux, a French paste that’s used to thicken numerous sauces, from white sauce to Espagnole. A roux is your go-to mixture for perfectly thick, lump-free sauces and is the basis for five of the mother sauces of French cuisine.
It’s such a basic technique that you won’t find a chef in a modern, pro kitchen that doesn’t know how to make a perfect roux. In fact, it’s so well known that most decent home cooks know how to make one, but not everyone knows there’s actually different kinds of roux.
There’s a classic white roux, there's a blonde roux, a caramelised, brown roux which is used for cooking Cajun dishes like gumbo. There’s even a red roux with tomato sauce added which is often used for thickening seafood dishes.
Classic White Roux
This is for your white sauce aka béchamel and cheese sauces. White roux is normally made using butter and regular white flour in equal parts. The butter is melted on a very low heat as flour is stirred and removed from the heat as soon the flour starts to bubble. The color should remain bright white as the flour is barely heated in a classic white roux recipe. Many places opt for skipping white entirely and using blonde roux as undercooked flour carries a stronger flavor.
Also made using butter and white flour but cooked a little longer so the flour starts to blonde in color. This is the go-to roux for all your Velouté and Espagnole sauces, it can actually be used in most of the mother sauces but be aware that blonde roux will give more color to a sauce.
The flour in a brown roux is cooked for much longer which gives the final, caramelized paste, a much nuttier, deeper flavor. Because the flour is cooked for longe at higher temperatures, butter is often replaced for brown roux with vegetable or peanut oil - fats with higher smoke points than butter.
The dark Roux is said to have been developed in the French colonies and is associated today with Cajun dishes such as Gumbo. It’s worth noting that the more you cook the flour in the fat, the less thick the roux actually becomes. Many people will add onions, peppers and celery directly to a roux in preparation for gumbo.
The Red Roux is essentially a blonde roux with tomato paste added and it’s usually used to thicken seafood sauces like Bisque or Couvillion, some will also go the red roux route for Gumbo.