I used a 3.5 quart slow cooker. Put the applesauce and sugar into the cooker, and add cinnamon and other spices. Cover the crockpot and set on HIGH for an hour, to warm it up and begin the cooking.
After an hour, prop the lid: lay two wooden spoons or chopsticks across the cooker insert, then put the lid on top. This will permit the evaporation needed to reduce applesauce into apple butter.
Set the cooker to LOW. After an hour or two, stir the applesauce, then replace the lid on its props. Allow the pot to cook, with the lid propped open, for 8-10 hours. It's okay to let this cook overnight.
You might want to put the entire process on hold for a while – this is no problem! Simply remove the chopsticks, set the cover back in place, and leave the slow cooker on LOW for an hour or three. When you’re ready to proceed, prop open the lid again, and evaporation will resume.
Stir the apple butter and check the texture. If you want a very smooth and silky butter, whiz the batch with an immersion blender.
In my last batch, the total time on LOW was about 12 hours. Every batch will be a little different, so check consistency and stop the evaporation when it’s firm enough for you.
TO CHECK FOR DONENESS: spoon out some of the apple butter, and then turn the spoon right over. The apple butter should not fall off right away, but should cling to the spoon for a bit. You can also plop a spoonful of the apple butter on a saucer and let it stand for a minute or two. Check carefully: if there is no rim of liquid that has separated out, the apple butter is ready to bottle and seal.
TO CAN: Prepare jars as usual. To seal the jars in waterbath or steam canner, process 10 minutes.