Place a small plate in the fridge/freezer to help testing the consistency of the jam later on.
Place a large pan or preserving pan over a medium high heat and add 250ml of water and the lemon juice.
1 large lemon
Add the sliced apples and give them a little mix.
Bring to the boil and then reduce the heat so they simmer for about 6-8 minutes. The apples will have softened by then.
Add the blackberries and the granulated sugar and thoroughly mix together.
500 g blackberries, 1 kg granulated sugar
Reduce the heat to low and stir again. Keep stirring until the sugar has fully dissolved so the jam will be lovely and smooth.
Once dissolved, increase the heat and simmer again for about 30 minutes until the jam has thickened in texture.
Retrieve the plate from the fridge/freezer and place a little on the plate. Using your finger, pull your finger through the jam. If it has set and the jam leaves little creases where your finger was, then its ready to go.
Carefully ladle/spoon/funnel the jam into sterilised jars filling almost to the top. The jars must have tight fitting lids that seal properly.
Cut a little disk of greaseproof paper the size of the lid and place inside each of the jars. When the jam has fully cooled, seal and place in the fridge or cool cupboard.