Depouillage is the French culinary term  which means "to skim fat"  which is done to remove the fat that rises to the top of sauces, stocks and other cooking liquid during cooking. Depouillage is simply and more easily done by placing the pot off-center on the burner and skimming the impurities as they collect at one side of the pot.

Depouillage or cleaning (skimming) of a sauce/stock (for soups)  is the most important process in building a sauce or stock.  

In making sauces, a cook that does not undertake this process or understand  its importance will end end up a sauce or stock that is full of impurities and fat.

To skim or clean the sauce, this procedure will help:
1. After the roux and stock are blended together, bring the sauce to a boil.
2. Reduce the heat and let the sauce simmer slowly. You will see the impurities accumulate on the surface.
3.  Skim the accumulation of impurities off

This process is a must when working with a roux sauce to have a fully finished sauce.

Straining of the sauce also improves the texture and increases the luster or sheen.  Straining will also Blend the liquid ingredients together. For best results, the use finest mesh available is necessary.

Depouillage is pronounced "Dep- oh-lahj".