Working over a large plate or bowl to catch the juice, remove the peel and pith from 2 of the oranges with a sharp knife, cutting down to the pulp in one operation.
Cut out each section from between the membrane and set aside.
Reserve the juice and add it to the juice of the third orange.
Strain and set aside Heat a large cast iron frying pan,dry, over a medium low heat for a few moments Add 3 oz butter and as soon as it starts to foam add the slices of liver, reduce the heat to minimum and cook very gently for no more than 2 minutes on each side, do not overcook, it must remain soft with no outer crust, and pink inside.
Liver continues cooking by its own heat when removed from the pan.
Arrange on a heated serving dish and keep hot covered with a plate.
Increase the heat to medium, deglaze the pan with the orange juice, incorporating the meat residue by scraping it up with a fork, season with salt and allspice, allow to bubble, then add the orange sections.
Tip the pan back and forth allowing the hot juice to flow over the fruit, do this quickly.
Remove the sections with a fork and place them around the meat.
Remove the pan from the heat, whisk in the remaining 1 oz of butter, cut into small pieces and pour over the liver.
Serve right away with small new potatoes, parselied and buttered or with garlic mashed potatoes and green peas.