Recipes are one thing. Methods are another. I'll talk about roux in some posts. Not just the method, but the science...because understanding that doesn't make you a better cook, but it answers the question of "why".
We know that roux is one type of oil and flour. We dissolve the flour in the oil to keep the flour from clumping together. As we heat it up what happens is the starch molecules in the flour start bonding together...kind of like forming long chains by holding hands. These bonds between the starch molecules are pretty strong so that the long strands are not breaking down as the roux is cooking. The heat is also cooking the flour and turning it darker like bread in a toaster. As we whip the roux or stir it, we're not breaking the long strands up but tangling them up. Roux thickens because it's limiting water movement...in a sauce or soup, for example.
As you're cooking the roux, it gets thicker as well as browner. At first it's real smooth and the color of peanut butter. But after it gets darker brown it gets grainy...like sand particles. What's happening is the carbohydrate strands are clumping up even more. This is when the roux will thicken the most.
At this point, I'm usually finished cooking the roux so I throw in previously chopped onions. This stops roux cooking by cooling the roux down. As I stir the onions, it gets very dark and very thick...almost solid. The onions have acid in them and the heat turns the acids into sugars which, in turn caramelize. That's why it gets dark. It gets thick because the onions have water which gets in the spaces between the carbohydrate strands and is trapped there. It sort of solidifies.
If you want a darker roux, don't throw in onions and keep stirring it. It will get darker and not burnt if you're careful. Eventually the heat will reach a point where it will break down the strands. Dark roux have better/different flavor but they don't thicken as much because the strands are now shorter and water movement is not as inhibited. (Less thickening)
Good, but the jar roux is very good and I even use Tony Chachere's dry powdered roux in a pinch. I use a commercial butter flavored oil at the cafe with general all purpose flour to make my roux there.
Blonde roux is butter or margarine with the AP flour. I try to incorporate as much flour as I can in a pound of melted margarine so I don't have to use a lot to thicken things. You have to cook the blonde roux for about 10 minutes. Until the flour gets a "nutty" smell. This happens before it starts turning brown. It's done when the flour is toasted some to keep the sauce or soup from changing color. This is important when you're using blonde roux in a cream (becamel) sauce or a milk based soup.
I know...but those jar roux come out of million dollar kitchens with great experimental chefs and food scientists perfecting the methods. They're really good.
