I grew up in the Mohawk Valley of Upstate New York, where apples abounded. In the autumn, we'd go to one of the local orchards to pick our own. The one surefire way to conjure up the flavor of the apples of my youth is by cooking them down into a rich, smooth apple butter. Slathered on an English muffin or swirled into a warming bowl of morning oatmeal, it transports me back in a single bite. Best of all, apple butter is possibly the easiest preserves to make. You don't even have to peel or core the apples, and you can do the entire thing in your slow cooker. Sealed up in half-pint jars, I can always have some on hand when I want to relive those chilly mornings among the apple orchards.
Thoroughly wash apples. If they seem waxy, scrub with a produce brush. Organic apples are recommended since you will be cooking them with the skins on. Quarter the apples and add them to your slow cooker. Add apple cider vinegar and cider or juice. Cook, covered, until the apples are soft.
Mash the apples with a potato masher until thoroughly pulped. Run the pulp through a food mill to catch the skins and seeds, passing a puree. If you do not have a food mill, press the pulp through a sieve.
Add dark brown sugar, maple syrup, ground cinnamon, nutmeg, allspice and salt. Cook, stirring occasionally to prevent scorching, until the apple butter darkens and it mounds on a spoon. Adjust sweetness and seasonings to taste. Store in the refrigerator for a month or water bath can for 15 minutes and store in a cool, dark place for up to a year.