Wash the liver well. Dice the bacon and fry in a saucepan until crisp. Remove and keep hot. Chop the onions and fry in the bacon fat (covered) until tender but not brown. Season with salt and pepper. Dust in the flour, add the stock and stir until boiling. Place the slices of liver on top, cover and simmer for ½ hr. Serve the slices of liver on a hot dish with the bacon on top and the onions heaped neatly at each end, sprinkled liberally with parsley.