Martha Stewart is making stock on PBS. She is using a small sieve to skim the foamy gray stuff that gathers on the top when you first start to simmer broth or stock, and she keeps referring to it, over and over, as fat. No! The grey scum is a form of protein, and it’s a completely different substance from the clear chicken fat (which a sieve wouldn’t be much help with).
Obviously, there’s fat gathering at the top of the stock as well, but you can easily wait until the stock or broth is finished before removing it (which Martha does). When you chill the stock, the fat will rise to the top and solidify, and you can easily spoon it off the top. If you need to use the broth immediately, and don’t have time to chill it, you can use one of those separators that pours from the bottom.
Another difference is that the foamy protein scum can only be thrown away. Some cooks save the chicken fat, as unhealthy as that sounds, and do things with it.
The fat and that protein foam are two different things, and someone presenting herself as an expert ought to know the difference. Martha should watch Alton Brown, who actually knows what he’s talking about.
It only occurred to me just now that there’s a joke to be made about Martha Stewart and her criminal treatment of stock. That wasn’t my original intention.