Bring milk to the boil, add rice, 2-3 tablespoons of sugar and 1 pinch of salt. Leave to swell for about 30 minutes over low heat, stirring occasionally. Wash, halve and stone the plums. Cut plums into thin slices.
Mix 4 tablespoons sugar and cinnamon. Stir half into the rice. Arrange rice and plums in deep plates. Sprinkle with remaining cinnamon sugar and pistachios.