Grease a 500 g (1 lb) loaf tin lightly and line the base and sides with nonstick baking paper. Blend the ricotta and cream cheese with the eggs, vanilla essence and caster sugar until smooth. Turn the mixture into the loaf tin and place in a small roasting tin. Pour hot water into the tin to a depth of 2.5 cm (1 inch) and bake in a preheated oven, 160°C (325°F), Gas Mark 3, for about 40 minutes or until lightly set. Lift the loaf tin out of the water and allow to cool in the tin.
Stud the orange with the cloves and place in a heavy-bottomed pan with the brown sugar, cinnamon and measured water. Bring the water to the boil, reduce the heat and add the plums. Cover and cook gently for 5 minutes or until just tender.
Lift out the plums and add the redcurrant jelly to the pan. Boil the liquid for about 2 minutes until reduced and syrupy. Remove the orange and cinnamon stick and pour the syrup over the plums. Let the syrup cool, then chill until ready to serve.
Remove the cheesecake from the tin, peel off the paper and cut into slices. Serve topped with the poached plums.