Here is a slightly modified recipe based on writings from the middle ages (or thereabouts). The tilting of the dish mentioned in the last couple of lines is an interesting technique which was used to distribute
flavours through the pie.
Finely chop onion and cook for about 5 minutes in a smear of oil until softened. Mix pork, onions, ginger and salt. Put this on the bottom sheet of pastry in a pie dish. Cut a small hole in the top sheet and cover the meat. Bake in a moderately hot oven for about 45 minutes. Combine vinegar and sugar with about 1 tablespoon of hot water, stir to dissolve sugar, then pour this through the hole in the pastry lid. Tilt dish from side to side and return to oven for a further 5 minutes. Serve hot or warm.