For the apple-blackberry jam, steam the sliced, peeled and cored apples until they are soft.
Heat the blackberries with a little water and then pass them through the liquidizer. It should yield 1 1/2 kg of puree.
Mix the apple pulp and blackberry puree with the jelling sugar and cook for about 5 minutes to make jam. Wash out the jars while hot, fill, seal and let cool upside down.