String the shank. Cover for two and a half hours with cooking salt. Remove salt and wash it. Put the shank with the vegetables, aromatic herbs and liquids into a vacuum-sealed cooking bag.
Cook in a steam oven for 16 h at 800C. Take the resulting liquid and reduce it, thickening it into a sauce with the butter. Heat the oven up to 2000C (heat only) and introduce the shank for 5 minutes, after brushing it with the sauce.
Repeat the operation until the desired colour is obtained.
Ideally, accompany with small roasted Coristanco potatoes.
Antonio Amenedo, Restaurante Pazo de Santa Cruz (Coruña Cociña)