I am a saucier at heart. The daily ritual of making demi has eluded me lately and I feel a void where this obsessive-compulsive task is missing from my everyday schedule. Not one chef I've ever worked for has ever made it the same way and the details hold glimpses into the heart of the chef in question (atleast for the French trained).
I start with fresh, not frozen bones if possible. The only vendor who carries them currently in the Chicagoland area that I know of is Lex Foods, the owner being John Lex. (847) 432-5741, BTW. He's related to the guys who run JDY, who should be able to get the bones from John if you're interested in the product. This isn't cheap, however.
I personally don't mind cutting hard bones with soft bones 50/50. Soft bones are cheaper and tend to run smaller. They're great for second washes or remoulage (the term for making veal stock from the same bones twice, often used to start the next batch of demi instead of water). The only issue with soft bones is that I can't find them fresh, and I'll only use them if I have to drive down my costs. Some brands are treated with sodium tripolyphosphate, which is a water retention chemical used in food processing to make the bones hold water and weight more and also helps with preserving the bones.
This sucks. I can smell it slightly, I swear. And when treated bones are roasted, they'll drop water, ruining the beautiful color you need to get from your veal stock. Crazy story somewhat off topic. For a while we were able to get ostrich bones at half the price of veal bones in the late 90's early 00's. Roasted and used in demi 50%, you couldn't tell the difference. I won't name names but you'd be surprised to know who bought them. Now the prices for ostrich bones are through the roof, as large soup companies caught on and buy almost the entire market. I shit you not. Effing ostrich.
Anyways, the next item is your mirepoix. I haven't weighed a batch in ages, and I personally go easier on the veggies as a whole (especially the celery). I like flavor, but primarily the flavor of the main ingredient in a recipe. Veal stock should taste like the distilled essence of a thousand dead baby steer. Nothing more, nothing less. The veggies should be peeled, and no ass ends of carrots or peelings make it into the stock.
Why you ask? Have you ever eaten the ass end of a carrot? Tastes like bitter carrot pukings! If you won't eat it, don't put it in your stock. It's a building block, not a fucking garbage pit! Next is the tomato product (I use paste). It's essential to giving body to your reduction, but I err on the light end. I will put four heaping kitchen spoons in for 100 pounds of bones. Michael uses 4#'s weighed out if I remember right, and Bernard uses a full #10 can. You can taste the difference, and you're able to reduce it more with less tomato. It is essential to getting the gelatin to take hold in a finished sauce though.
Speaking of gelatin, a few pig's feet thrown in at the end helps too. As for color, I will brulee my onions by cutting them lengthwise and charring the shizznit out of them. Your stock will never pick up any burnt notes, and the end product is worth seeing. On the other veggies being cooked, caramelization is essential, but not too much. Deglaze with red wine, but don't use too much. Again, it's veal stock, not effing bordelaise. Also, make sure you start with cold water or remoulage and bring quickly to a simmer. That gives a level of clarity that's desired.
Thyme, parsley, peppercorns, and fresh bay leaves finish the stew. Don't forget to skim, all the time! Re-emulsified fat kills a stock if made in the western tradition. The Chinese do some beautiful things with reincorporating fat into their stocks, but it will make an unappetizing demi with an ugly color and whorish taste. If you like tasting whores, go eat at the docks, not where I hang my hat. Cook overnight.
When straining for further reduction, save the bones and make stock out of them to start your next batch. And obsess! There's always another step to be taken to make a better product.
A sushi chef once told an apprentice, "The sushi is never perfect until all the rice is pointing the same direction." The lesson being that there's always something to improve on, no matter how good you are at the task.