1 lb of roux is used per gallon of liquid
A roux can be made from any type of fat, depending on what your soup or sauce needs.
Clarified butter is usually preferred for its flavor. Clarifying butter removes the water, milk solids and impurities. Regular butter can be used.
Margarine has a lower cost, but the flavor is different. Usually it is not used when making sauces.
Animal fats can be used when their flavors are appropriate for the sauce or soups. They are stronger, but do provide extra flavor.
Oil and shortening can be used, but they add no flavor.
Bread flour, all purpose flour, cake flour or wheat flour can be used.
Cake flour has the best thickening power, however bread flour and all purpose flour are just fine.
There are 3 types of roux
White Roux is cooked for a short amount of time, to cook out the starchy taste of the flour. You should stop cooking it as soon as it has a "chalky and slightly gritty appearance."
White roux is used for Béchamel and other white sauces.
Blond Roux is cooked for longer than a white roux, until the roux becomes a little darker.
Blond roux is used for Velouté and other white sauces.
Brown Roux is cooked until a darker color and nutty aroma has formed. You'll need to cook it over low heat to prevent burning. It will take a while to make a brown roux.
Brown roux is used for Espagnole and other brown sauces.
Use a saucepot to make your roux.
Basic Procedure for Making All Roux (Gisslen, Professional Cooking, Seventh Edition Page 174)
- Melt fat
- Add correct amount of flour and stir until fat and flour are evenly mixed.
- Cook to required degree for white, blond, or brown roux.
The next part is how to incorporate the liquid into your roux. Usually this is in the recipes for sauces, but I'll review it.
Now you'll add the liquid. You can either add the liquid to the roux, or the roux to the liquid. It doesn't really matter, but usually you'll be adding the liquid to it.
Slowly pour your liquid into the roux. Make sure you're continuously whisking so that the starch doesn't gelatinize too quickly and form lumps. You can either use a hot or cold liquid.
Recipes and information come from Professional Cooking, Seventh Edition, Wayne Gisslen; and myself.