Beurre de pomme incroyable

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.

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.

Cook on High with the lid off until the moisture evaporates and the volume reduces by about half, overnight to 24 hours.

Stir sugar, apple cider vinegar, cinnamon, cloves, and allspice through the apple puree.

Continue cooking on High until mixture mounds on a chilled plate without any water separating from the edges, another 2 to 6 hours.

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.

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.