While originally brown sauces were espagnole and demi-glace, now they have expanded to include jus lie, pan sauces, and brown stock reductions. 

To make espagnole you should make a brown veal stock, then add more roasted mirepoix, and aromatics (like a bouquet garni) and thicken it with a roux.  Demi-glace is a mixture of half espagnole and half brown stock that is reduced by half to create a thick.  Jus lies are brown sauce reductions thickened with a starch slurry.  Pan sauces are like gravy, made with the drippingsin the bottom of the pan. 

The most important step in making brown sauce is to create a high quality stock. 

Step 1:  Brown the Bones and mirepoix

Step 2:  Deglaze the pan and use the deglazing liquid in the pot to simmer the bones and mirepoix.

Step 3:  Simmer the stock.

Step 4:  Add Aromatics to stock, Skim, placing pot off center of the burner will help impurities coolect to one side of the pot. 

Step 5:  Strain stock, return to light simmer if needs to be reduced more.

Step 6:  Thicken sauce with desired thickening agent

Tips:  When storing sauce put plastic wrap on the surface of the sauce, this will prevent a thick film from forming on the top of the sauce. 

Many sauces can be created from this sauce.  Commom derivatives, flavor profiles, and common pairings of Brown Sauce to be posted soon on a seperate link.