Smear the shank well with oil.
Oil a sheet of foil well and wrap the shank in it, with the edges raised so the sauce doesn't spill out during baking.
Put in the fridge for 24 hours.
Bake 2 hours 30 min. in a preheated 392°F (200 °C) oven, while periodically pouring in a little water to the tray in which it's baking.
Serve with mashed potatoes and the sauce released in the foil during baking.