This one is a beast to make, but it will make 3-4 servings of the base for some of the best sauces you'll ever taste. This is, essentially, a stock that's cooked down until the natural gelatin thickens the sauce, but you'll have to make the stock yourself as store bought stuff doesn't have the gelatin or the depth of flavor that you need. You'll also need a big soup pot to hold everything.
8 lbs beef bones, a mix of marrow bones and joint ends (you don't want the typical soup bones that are a little chunk of bone with a bunch of meat around it)
1 lb onion, rough chopped
1 lb carrots, rough chopped
1/2 lb celery, rough chopped
8-10 sprigs parsley
1 bay leaf
3 cloves garlic
1 t dried thyme
Roast the bones in a 400 degree oven for 3 hours. Add the onions, celery and carrot plus 2 cups of cold water to the roasting pan (carefully, there may be some splattering from the hot fat in the pan) with the bones and return to the oven for another hour.
Transfer all of the bones and veggies to a soup pot as well as all the juices and anything you can scrap off the pan, add the rest of the ingredients and add enough water to cover everything by an inch or two. Simmer for 8 hours, adding water occasionally if needed, and skimming off any scum that floats to the surface.
Kill the heat and strain out all the veggies, bones, and other solids and pitch them, then chill it down in the fridge to solidify the fat so it can be easily removed. Now take the stock and bring it to a high boil for three hours or so until the volume is reduced to about a pint.
The finished glace de viande can then be turned into specific sauces: add in the drippings from a roasted chicken, some poached garlic, and a few tablespoons of butter and you have a sauce for the chicken; use some burgundy to deglaze the pan after cooking some steaks, then add in the glace and a couple tablespoons of butter and you have bordelaise sauce for the steak. Leftover glace de viande freezes well.