I made two batches in my slow cooker.
The first with a ton of sugar and the second with maple syrup and honey. They are both delicious. I cooked the sugary one longer and it came out thicker.
Apple Butter one
16 apples, peeled and sliced
3 cups sugar
3/4 cup apple cider
2 T cinnamon
1 t allspice
¼ t nutmeg
pinch salt
Apple Butter two
22 apples, peeled and sliced
¼ cup honey
1 cup maple syrup
1 1/4 cup apple cider
3 T cinnamon
2 t allspice
½ t nutmeg
pinch salt
In the slow cooker on high for a couple hours, then low overnight and/or the rest of the day until the apples cook down to a sauce and the pooled liquid evaporates. Stir occasionally. I cooked my first batch on and off for two days. The cooker went off a couple times and when I turned it back on I put it on high for a bit, then turned it back to low. The second batch I cooked for about 24 hours and would have done it longer as it turned out a little thin. I am sure the sugar also adds to the thickening process.