Blackberry and Apple Jam

• 2 kg (4½ lb) blackberries, washed
• 300 ml (½

Place the blackberries in a large saucepan with half the water and simmer gently until soft. Put the apples in a preserving pan with the remaining water and simmer gently until soft. Pulp with a wooden spoon or a potato masher. Add the blackberries and sugar to the apple pulp, stirring until the sugar has dissolved, then add a knob of butter, bring to the boil and boil rapidly, stirring frequen