Stir the cornflour into the water to dissolve, then pour into a small saucepan. Add the apple, prunes, cinnamon, ginger and lemon juice and zest. Cover and cook on a low-medium heat for 5 minutes or until the apple is softening.
Stir in the pear, cover and cook for a further 2–4 minutes. Uncover and continue to cook until the fruits are soft and cooked and cradled in thick juices (add a spoonful of warm water if necessary).
Take off the heat, stir in the sweetener to taste and serve.