Wash, peel, core, and dice apples into pieces.
Add apples, 1 cup granulated sugar, 1 cup brown sugar, cinnamon sticks, and cloves to the slow cooker. Cover with the lid and cook on LOW for 10 hours.
After 10 hours of cooking, fish out the cinnamon sticks and cloves (as much as possible). puree the tender apple pieces using a hand blender. [See recipe notes]
Do a taste test and see if you need more sugar. Add the required sugar and cook on LOW for another 2-3 hours to thicken the apple butter. [Keep an eye out to see whether your desired thickness is reached during the last 1-2 hours of cooking] Once your desired thickness is reached, turn off the slow cooker and allow the butter to cool down.
Transfer to storage containers. Refrigerate leftovers.