Return the osso buco to the liquid and simmer till warmed through. Serve.
Feel free to substitute the meat with short ribs, lamb shanks, or oxtail. Follow every step, only adjusting the cooking time till tender.
Demi-glace can be purchased at most good butchers these days. If you can't find it, and don't want to make your own, feel free to omit. Replace with beef stock.