Preheat the oven to 320°F (160°C) with top and bottom heat (convection is not suitable).
Rinse the lamb shanks under running water, remove any excess tendons and pat dry with kitchen paper. Rub with salt and pepper.
Peel the shallots and garlic cloves. Finely dice the shallot and slice the garlic. Clean and peel the celery root and carrots and cut everything into small cubes. Strip the rosemary needles from the branches against the growth direction and chop them finely.
Heat oil or butter in a casserole dish and brown the lamb shanks on all sides. They should get a nice roasting aroma. Remove the shanks from the casserole dish and set them aside.
Now first add the shallots to the hot casserole dish and fry them briefly. After 3 minutes, add the celery root and garlic and also fry briefly. Add the shanks back to the casserole dish and add bay leaves, rosemary, and raisins. Pour everything with the red wine and the lamb stock.
Close the casserole dish with a lid and let the lamb shanks simmer in the oven for 2.5 hours.Baste the shanks with some braising liquid several times. After braising time, remove the lid and let them continue to roast for another 30 minutes.
Remove the shanks from the casserole dish, cover with aluminum foil to keep warm and set aside.
Strain the braising liquid from the casserole dish into a pot.Add the cream and let the stock boil down a bit. Season the red wine sauce well with salt and pepper. Now add the butter and bind the sauce with it.
Arrange the lamb shanks on a platter and pour the red wine sauce over them or pass the sauce on the side. Finely chop the parsley and sprinkle over the lamb shanks.