Preheat the oven to 180°C, (160°C for fan ovens), Gas Mark 4.
Halve and stone the plums then slice into quarters then simmer gently in a pan with 3tbsp water and 2tbsp sugar for about 10 minutes until soft.
Beat the remaining ingredients in bowl until smooth to make the sponge. Spoon the plums into the tins and top with the sponge and smooth over the tops. Put the tins into a deep roasting tin.
Pour hot water from a kettle into the roasting tin until about halfway up the sides of the puddings. Cover the whole tin with foil, carefully transfer to the oven (taking care to keep the tin level) and bake for 20-25 minutes until light golden and risen. Serve with Carnation Evaporated Milk.