There ain't a lot of glamor in demiglace. It takes a lot of time. And a helluva lot of stock. No talent, very little technique, and if you save your kitchen scraps, very little expense--but time and stock you'll need in aces. And even once you've got a few rounds of demi finally in your clip, you still need something to cap, which means you've still gotta cook dinner. Now the good news: demi's easy to preserve frozen in ice cube trays, and a small amount of it will enhance the profile of your sauces immeasurably. Hell, it already is a sauce! With patience, your efforts will be spectacularly rewarded, for demi will put most any at-home hobbyist cookery on the fast-track to becoming truly great bistro fare. A nugget of demi, mind you, is the highly concentrated crystal of flavor slowly extracted from some of the best stuff out there: roasted bones, shaggy meat scraps, aromatic root vegetables and herbs. It might even be said that a cache of adoringly prepared demiglace confirms the kitchen workman's faith in the honesty of taste. At least, that's the sort of food-based, secular spirituality you'll start proselytizing after watching hours of slow reduction on your way to this blue-collar delicacy.
In the spirit of reduction, let me summarize the preparation: begin by making sauce espagnole, strain that, combine the resulting liquid with an equal portion of stock and reduce by half. That's it. Traditionally one uses veal stock, but in its absence, I'm working with beef stock tonight. Quantities are tough to estimate for this recipe since it depends on how much stock you have, so as usual, I'll stress ratios over quantities. The recipe in The Professional Chef calls for a total of two gallons (eight quarts) of stock to produce two quarts of demi. In my experience, this ratio basically holds up, so you can look forward to demiglace in the amount of one quarter of the quantity of stock you begin with. Given the time involved, I'd recommend making as much demi as you can in a batch. That'll free you up for more glamourous pursuits.
Sauce espagnole is a mother sauce, which means that chefs back in the day were 'bout it. Not so much anymore. Anthony Bourdain says nobody makes it these days, and so he offers a roundabout shortcut to demi that amounts to reducing stock and wine with some shallot. We're keepin' it classical here, though, so do start with sauce espagnole.
Predictably, sauce espagnole begins with mirepoix (50% onion, 25% each of carrot and celery): sauté the onions till browned, then add the carrot and celery. Let them all get some color, then throw in some tomato paste (a few healthy spoonfuls; remember, you can make your own by pureeing a tomato or two and cooking out as much of the water as you can). Let the mirepoix and toms get to know each other over medium heat. Your house should smell great by now.
While the vegetables are simmering, start your roux. Mix either oil or clarified butter with an equal amount of flour and cook over medium heat. Stir regularly until chocolaty brown. You'll only need about a cup of roux for about a quart of sauce espagnole. It's important to cook your roux at this point for two reasons: first, a cooked roux has less thickening power than its uncooked counterpart, which means the sauce will thicken without becoming too gelatinous, and, second, a cooked roux will deepen the color and flavor of the finished product.
Once the mirepoix and tomatoes have turned a rusty brown color, add enough stock to more-than-submerge them. The Professional Chef calls for 1.5 gallons of stock to make 1 gallon of sauce espagnole, which gives you some sense of the proportions you're dealin' with. Once you have the stock in, bring it up to a simmer and whisk in the roux. Add a few whole peppercorns and some fresh herbs (thyme sprigs are great), too. Simmer for an hour, skimming fat off the top as needed.
To finish the sauce espagnole, strain through a double thickness of cheesecloth slung over a colander. Make sure you've got a pot to catch the sauce down below the colander when you start pouring. Or you're ganna be pissed.
Next, combine the strained sauce espagnole with an equal portion of stock. Reduce by half. Skim the fat. On low heat, this step took me about and 90 or so minutes. Strain it when you're done for clarity. Allow the demi to cool, then freeze in ice cube trays. And. You're. Done.
Demi is a sauce, so you could just thaw a cube or two and throw it on beef, chicken, pork, lamb, etc. You can also use it to deepen the flavors of soups. And here's how you can make a simple sauce using the pan encrustations left from searing pork, lamb, or most other meats: sauté shallots in the same pan you seared the meat in, sprinkle in a bit of flour, then deglaze with just enough red wine to coat the bottom of the pan. As the wine reduces, throw in a cube or two of demi. Season with salt and pepper. Taste, adjust.
They say Champagne is the only wine that goes with everything. Maybe so; but it's not the only sauce that enhances almost anything. In its smooth subtlety, demi, too, has earned an honored place in the pantheon of epicurean delights. Unlike Champagne, however, demi does it with roots and bones. It will win few beauty contests. But by turning kitchen scraps into the most important of French sauces, perhaps you'd agree that demi's about as close as Western civilization has come to alchemy thus far.
