I often take the easy way out and work with white roux, usually mixing it 1:10 for a sauce, and using the warm liquid into hot roux method. Tonight I needed a more toasted taste. I was afraid to try dark roux outright, and went for brown roux. "The professional chef" gives a bechamel recipe with 1:10 (white roux to milk) and an espagnole recipe at 1:8.5 (white roux to stock), so I thought I'd be on the safe side with 1:7.2 (brown roux to stock). The result was much thinner than I expected, I had to emergency-bind it with arrowroot.
So, I would like to know, what is the correct ratio for roux? Let's assume that I am thickening the same liquid (e.g. beef stock), and I know how thick a 1:10 mix of white roux and liquid gets. What ratio of blonde, brown and dark roux to liquid creates the same viscosity as 1:10 white roux?
Best Answer
My understanding is that the ratio shifts from 10:1 (liquid to roux) for a pale roux, up to about 5:1 for a nutty brown roux, with a somewhat linear relationship between the two extremes. A dark brown roux has very little thickening power, mostly they are used for flavor more than actual work-a-day thickening.
The problem may not so much in the roux ratios, but in other ingredient variations. For instance, if you are using a traditional 3:2 flour:fat roux, and your fat is butter, make sure you are using clarified butter, or that you are allowing most of the water to cook out of the butter before adding the flour - excess water in the roux will break down some of the starches and reduce the thickening strength.
Finally, there will be some variation no matter what - you can always make a little extra roux in a second pan to integrate if necessary.