Cut a pocket into each slice of liver. Clean and wash the peppers and dice 1/2 pods each. Mix with breadcrumbs and egg and season to taste with salt, pepper and thyme.
Pour the mixture into the liver pockets and close the opening. Turn the liver pieces in flour and fry in hot fat for 3 minutes on each side. Cut the remaining peppers into strips, onions into rings, fry briefly in the fat, then add 1/4 litre of hot water and thicken the stock with the gravy.
Cook for 10 minutes.