Melt the butter in a heavy pan and fry the meat with the leeks and garlic till the vegetables are slightly softened and the meat lightly browned. Add the barley, water, vinegar, bay leaves and seasoning. bring the pot to the boil, cover it and simmer gently for 1 1.5 hours or till the meat is really tender and ready to fall from the bone. Add the sage and continue to cook for several minutes. Adjust the seasoning to taste and serve in bowls-the barley will serve as a vegetable.