Ballotines are usually poached very slowly in water, stock or another flavoured liquid, then left overnight and served cold. Cooling the meat in its wrapping allows it to set in the cylinder shape and as a result makes slicing easier. Ballotines can also be braised on a bed of vegetables, in which case they are rolled and tied but left unwrapped and generally served hot.
Weigh the ballotine and calculate the cooking time, allowing 20 minutes per 450 g. Place in a pan, cover with stock and weight it down if necessary. Bring to the boil, then lower heat and poach for the calculated time.
Let the ballotine cool in the liquid. Lift out of the pan, cut string and unwrap. Snip one end of the thread and pull it out. Slice the ballotine and serve cold, with a garnish of your choice.