Without a dark stock, there are no dark sauces in classic French cuisine. And it is precisely the handcrafted sauces that give a dish the necessary something. It was not without reason that the "sauciers", i.e. the sauce cooks, were the "primi inter pares" in the restaurant kitchen.
So here is the production of a dark veal stock, which is indispensable for the production of strong (meat) sauces. Even a game jus is often infused with a portion of veal stock.
Funds can be frozen or boiled down . . .