Cut the fruit into large chunks. Process the apples and pears in a food processor, working in batches, until finely grated. Transfer the fruit to the slow cooker.
Sprinkle in the brown sugar, apple juice, molasses, allspice, cloves and salt, and add the cinnamon sticks. Cover and cook 4 to 6 hours on high heat.
Remove the lid and reserve the cinnamon sticks. Carefully return the fruit, in batches, to the food processor and process until smooth. Transfer the processed fruit back to the slow cooker along with the cinnamon sticks. Continue cooking on high until thick and spreadable, another 2 to 4 hours. Allow the mixture to cool before transferring to sealed airtight containers.
Refrigerate up to 2 weeks or freeze up to 3 months.