I normally make this with venison, but beef, chicken, duck, goose, pheasant, quail, chukar, turkey all work. Lamb can get a little smelly in this process, and pork works, but isn't common.
Salt the meat and bones well. Set aside for 15 minutes while you heat the oven to 400°F. Put the meat and bones in a large roasting pan and cook at 400°F for 1 hour, or until well browned.
Meanwhile, toss the silverskin and cartilaginous bits into a large stockpot. If you have feet, chop them roughly, or score them all over with a knife. This opens the feet up to the broth, so all that gelatin can get into it. This is what makes the concentrated broth set up solid. Do not skip this. Put the feet in the stockpot, too.
Once the meat and bones are roasted, put them in the pot and cover everything with cold water almost all the way to the top. (cold water + cartilaginous bits = better gelatin later.) Turn the heat to medium-high and cover the pot. You need to be around as this heats up, because this is the one danger spot: The broth cannot boil. If I have other things to do, I don't cover the pot and I only set the heat to medium. This way it can take an hour for the broth to hit a simmer, and I don't have to stand there watching it.
Skim any froth that surfaces. Do this as many times as needed. As I mention above, I let the broth cook at the steaming point until I go to bed, then drop it all the way down, cover the pot and let it steep like tea overnight. You need a minimum of 4 hours, though, and 12 isn't too much.
Once the meats have simmered, add all the vegetables, herbs and spices. Simmer this for 90 minutes to 2 hours.
Strain the stock. Put paper towels in a strainer and set the strainer over a large bowl or pot. Ladle the stock through this to remove all debris and particles.
Clean your pot and return the broth to it. Bring this to a bare simmer, then drop the heat back to the steaming point. Let this cook down slowly by at least half, and two-thirds to three-quarters is better. You will need to skim it again.
In the end, you should have a clear, thick broth. You'll want to strain it once more, exactly how you strained it initially, through the paper towels. Pour the finished glace de viande into small containers, and refrigerate. It should set up and become a gelatin.