Once the stock boils, it is essential to skim it thoroughly and keep it cooking at a bare simmer. Both stocks employ mirepoix and a sachet or bouquet garni to round out and add complexity to the stock's flavor. Once both stocks are done cooking, they are identically strained and then cooled in an ice water bath. So far, so much the same. It's in the color and the taste.
White stocks are clear to light yellow while brown stocks are brown.
In terms of flavor, high quality brown stocks have a completely different flavor profile. Thus the first step in making a brown stock is to cook the ingredients until they attain a light caramelized color. This will add to the surface area of each bone and thus give more color and flavor to the finished stock. Place the bones, only 1 layer thick, in a heavy roasting pan. Place the pan in a 350 degree oven and cook until they are nicely browned and not burned.