Rub 75 g (3 oz) margarine into the breadcrumbs and Parmesan to form a paste.

Score the surface fat of the pork and press the cheese mixture well on to the fat.

Put the pearl barley and stock into a roasting tin. Put the pork joints on a rack over the tin. Cook in the oven at 180°C (350°F) mark 4 for 2 1/2 hours. Cover after the first hour. In a separate tin put the crackling strips into the oven, and raise the temperature to 200°C (400°F) mark 6.

Transfer the pork to a serving dish and keep warm.

Melt the remaining margarine in a saucepan and lightly fry the leeks. Stir in the flour and cook for 1 minute before adding the barley and juices from the roasting tin. Remove from the heat and gradually add the milk. Bring to the boil, simmer for 2 minutes and season. Serve with the carved pork.