Preparation:
wash and dry the pork shoulder and put it in a saucepan with high sides, but not too wide.
Cover flush with cold water, bring to a simmer, skim off the froth, then add the vinegar, salt, pepper, onion, celery, and bay leaf. Bring back to the boil and from that moment simmer, over medium heat, for about 2 hours. Remove the meat from the stock, cut into thin slices and arrange these on a serving dish.