For the pork shank
In a pan put some oil, chopped shallots, rosemary and sage and brown everything.
Once get brown, put the pork shank, cover with beer, lower the heat and cook for 40 minutes.
Once ready, remove the shank, put in a plate and cover with film to keep warm.
Keep the sauce over low heat until it is reduced and put away.
For the puré
Boil the potatoes in their skins for around half an hour until they get very soft.
Peal them hot and put them in a pan, add butter, milk, salt, pepper, nutmeg and a spoon of liquid smoke.
Mix over low heat until a thick cream is obtained.