Fry the bacon or pancetta in a little oil and butter until well cooked and then remove any excess fat from the pan. Remove the tops from beans, but there’s no need to take off the tails. Put the beans and the whole pears on top of the bacon, cover with 500 ml water and the wine and vinegar, but do not stir. Cover the pan with a lid and leave to simmer for about 40 minutes, or until the pears are cooked through.
To serve, arrange a pile of beans and bacon on each plate and top with a whole pear. Boil the sauce in the pan to reduce by about half, season with pepper and add the chocolate. Pour some of the sauce over each pear and sprinkle the beans with a grating of nutmeg and some parsley.