According to "La Cuisine Anglaise" , you take a small loaf of bread and cut off the two ends, then you take cut out the center of the loaf so that you have to halves about half an inch thick....
Ham,cheese,jam,penut Butter, Marmite, chocolate spread and egg mayonnaise.make a marmite sandwich, then boil an egg, shell it and slice it. put the egg in with the marmite! yumm!