Made of equal parts flour and fat mixed together and slowly cooked over low heat, roux is used to thicken stews, soups, and sauces.
Take a look at these tips for creating a Roux.
Step 3. For a light roux, use butter instead of fat. Cook and stir for about 10 minutes. Light roux is light reddish-brown in color and is used to thicken cream and white sauces and light soups.