Prepare the Apples: Peel, core, and roughly chop all the apples. Don't worry about making the pieces uniform; they will break down completely.

Combine Ingredients: Place the chopped apples in the pot of a large slow cooker (at least 3.5-litre capacity). Add the light brown sugar, granulated sugar, apple cider, apple cider vinegar, cinnamon, nutmeg, allspice, cloves, and salt.

Stir Well: Give everything a thorough stir to ensure the apples are evenly coated with the sugars and spices.

Slow Cook: Secure the lid and cook on LOW for 5-6 hours or on HIGH for 3 hours. By the end, the apples should be incredibly soft and the mixture will have darkened considerably. Stir it once or twice during cooking if you can.

Blend Until Smooth: Once the apples are completely tender, use an immersion blender to blitz the mixture directly in the slow cooker pot until it is perfectly smooth and velvety. If you don't have one, carefully transfer the mixture in batches to a countertop blender and blend until smooth before returning it to the pot. What works best for me is the immersion blender—it's much less fuss.

Thicken the Butter: This is a crucial step. Remove the lid, or prop it open with a wooden spoon to allow steam to escape. Continue to cook on LOW for another 1-2 hours, stirring occasionally, until the apple butter has thickened to a rich, spreadable consistency. It should be dark brown and mound on a spoon.

Jar the Apple Butter: Carefully spoon the hot apple butter into hot, sterilised jars, leaving about 1cm of headspace at the top. Seal immediately.

Cool and Store: Let the jars cool completely at room temperature. You may hear a 'pop' as they seal. Once cool, store them in the refrigerator.