In a large preserving pan, combine the water and chopped apples. Simmer over low heat for about 5 minutes until the apples soften.

Add the blackberries to the pan, increase the heat, and bring the mixture to a boil. Let it simmer gently for about 15 to 20 minutes until the fruit softens.

Take the pan off the heat and gradually stir in the sugar until fully dissolved.

Return the pan to low heat, stirring occasionally to ensure all the sugar is fully dissolved. Once dissolved, increase the heat and bring the mixture to a rapid boil. Cook for 10 minutes, stirring regularly.

Remove the pan from the heat and test the jam by placing a large spoonful onto a chilled saucer. If the jam wrinkles after a few minutes, it’s ready. If not, continue boiling for another 2 minutes and retest.

Skim off any foam with a slotted spoon, then stir in the butter to eliminate any remaining foam.

Carefully ladle the hot jam into sterilized jars, seal immediately, and let them cool. This recipe yields approximately 4 pounds of jam.