Recipe yields 8 pint jars.

MAKE THE PEAR BUTTER

• Peel, core, and quarter pears. 
  12 pounds ripe pears
• Place pears and apple juice in a slow cooker or in a large stock pot.
  3 cups apple juice
• For slow cooker: Cook for 3-4 hours on high or until the pears are very soft. 
• For stovetop: Bring to a boil over medium-high heat. Reduce heat and simmer, stirring frequently for about an hour or until pears are very soft. 
• Use a potato masher to break up chunks of pear. 
• Working in batches, run cooked pear pulp through a food mill, sieve, or chinois. 
• Return pear puree to slow cooker or cooking pot. 
• For slow cooker: Tilt cover to allow steam to escape. Cook for another 6-8 hours on low, or until pear butter is thick and holds its shape on a spoon. Add spices.
  2 teaspoons cinnamon, 1 teaspoon ground nutmeg, ½ teaspoon ground allspice, 2 teaspoons vanilla
• For stovetop: Simmer over low heat, stirring frequently for 2-3 hours until thickened. The pear butter should hold its shape on a spoon. Add spices.

PREPARE FOR CANNING

• Wash the jars you'll use, making sure each is clean and free of nicks in the rim, which could impede sealing.
• Wash the lids and rings in hot soapy water. (If you're using non-Ball brand lids, prepare as suggested by manufacturer.)
• Place empty jars in a canning pot or large stock pot with enough water to cover by an inch or two, cover pot, and set on high heat. It can take awhile for the water to heat, so get it started about 30 minutes before pear butter is done.

CANNING

• Ladle hot pear butter into jars, leaving 1/4" head space. A canning funnel makes this easy.
• Wipe jar rims to remove any fruit mixture that may have spilled. A clean rim is essential to a good seal.
• Place lids centered on the jar rim. Screw bands on finger tight.
• Use a jar grabber to gently submerge jars into hot water in the canning pot. Water should cover the top of the jars by an inch. The water will cool somewhat in reaction to the addition of the jars. Return the water to a simmer and then set the timer.
• Process for 15 minutes 0-1,000 feet altitude; 20 minutes 1,001-6,000 feet; 25 minutes over 6,000 feet.
• Remove jars from water using the jar lifter and transfer to a solid, towel-covered surface. Listen for the popping sound of the lids sealing (a canner's favorite sound!). Allow to cool for 24 hours.
• Check seals. Lids should be solid and pulled down tight. (if they flex and pop, the jar didn’t seal; put unsealed jars in the refrigerator and use those first).
• Remove rings and wash outsides of jars. Store in a cool dark place.