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1
Combine apples and apple juice in a stockpot; bring to a boil. Reduce heat and cook at a simmer until apples are soft and mushy, 20 to 30 minutes.
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2
Spoon apples into a food mill and process into puree while discarding the cores and peels remaining in the mill. Transfer process apples to a slow cooker.
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3
Cook on High with the lid off until the moisture evaporates and the volume reduces by about half, overnight to 24 hours.
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4
Stir sugar, apple cider vinegar, cinnamon, cloves, and allspice through the apple puree.
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5
Continue cooking on High until mixture mounds on a chilled plate without any water separating from the edges, another 2 to 6 hours.
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6
Sterilize the jars and lids in boiling water for at least 5 minutes. Pack the apple butter into the hot, sterilized jars, filling the jars to within 1/4 inch of the top. Run a knife or a thin spatula around the insides of the jars after they have been filled to remove any air bubbles. Wipe the rims of the jars with a moist paper towel to remove any food residue. Top with lids, and screw on rings.
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7
Place a rack in the bottom of a large stockpot and fill halfway with water. Bring to a boil and lower jars into the boiling water using a holder. Leave a 2-inch space between the jars. Pour in more boiling water if necessary to bring the water level to at least 1 inch above the tops of the jars. Bring the water to a rolling boil, cover the pot, and process 5 to 10 minutes.
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8
Remove the jars from the stockpot and place onto a cloth-covered or wood surface, several inches apart, until cool. Once cool, press the top of each lid with a finger, ensuring that the seal is tight (lid does not move up or down at all). Store in a cool, dark area.
