A roux, pronounced roo, is simply a mixture of equal parts fat and flour used to thicken liquid. The fat used can range from oil, butter, even bacon grease. Start by heating your fat in a large pan over medium heat. Once the oil is heated, gradually sprinkle in an equal amount of flour.
... the darker the color and the richer the flavor. There are four types of roux. Each is used for specific reason.
A white roux is used solely for thickening. It is cooked just long enough to get rid of the raw taste of the flour and does not add any distinct flavor to the dish.
A blonde roux adds just a slight amount of flavor to the dish. It should resemble the color of caramel. Used for making gravy.
Some people also refer to this as peanut butter roux. It has a slightly nuttier flavor than the blonde roux.
Because it is cooked the longest, it has a very distinct nutty flavor. It should resemble the color of chocolate.