Prune Mould

From 1922:

Wash, soak, and boil ½ lb. of prunes in a pint of water. When soft break them, take out the stones, add the juice and rind of a lemon and a few drops of cochineal. Simmer for 20 minutes. Dissolve ¾ oz. of gelatine in a little water, and add it to the prunes. Turn out when set firm, and serve with custard.