Your first step is to cook and puree the pears to make pear sauce.  The most basic way to do this is to peel, stem and core the pears by hand and then cook them in a thick bottomed pot or enameled dutch oven, along with a small amount of water for 30-40 minutes until soft.
Alternately, you can just coarsely chop the pears and cook them with skins and cores intact and then use a food mill to remove the seeds and cores.  I cooked my pears in an instant poton high pressure for 10 minutes and then used a kitchen aid food mill attachmentto remove the seeds for start to finish pear sauce in about 30 minutes, mostly hands off.

If you didn't use a food mill, process your pears in batches through a food processor or use an immersion blenderto thoroughly blend the pears into pear sauce.

Return the mixture to your dutch oven or pot and add whiskey and maple syrup.  Simmer, uncovered until the mixture thickens, darkens in color and holds its shape on a spoon.  I like to cook it until you can pull the spoon across the bottom of the pot and it's thick enough that it takes a while for the mixture to fill the gap back in.

If canning, ladle the hot pear butter into jars, leaving 1/4 inch of headspace.  Remove air bubbles, lid, and band jars.  Process in a water bath canner for 10 minutes, adjusting for altitude.