Dissolve the sugar in the water then bring to the boil and boil for a few minutes to make a syrup. Add the plums and cook gently for about 8–10 minutes to a lumpy, marmalade consistency.
To make the sponge, mix the butter and sugar together until almost white, then add the insides of the vanilla pod and beat in the eggs and egg yolk. Fold in the flour, lemon juice and zest. Spoon some of the plums and their syrup into the bottom of the moulds or basin. Cover with the sponge mix to come three-quarters up the sides. Cover with buttered foil and place in a steamer or a pan half-full of hot water. The small puddings will only need 40 minutes in the hot steamer, the large pudding will need 1–1½ hours.
When cooked, turn the puddings out on to a plate or plates and spoon some more of the hot Victoria plum syrup over each portion. The dish is now ready to serve and will eat well with either fresh cream or Anglaise Sauce.