Step 1

In a food processor, pulse pears and apples until fruit is chopped into very small pieces. Transfer the fruit to a large Dutch oven or other heavy-bottomed pot. Stir in lemon juice, cinnamon, allspice, ginger, cloves, nutmeg, pectin and butter.

Step 2

Bring to a rolling boil over medium-high heat. Add sugar and stir to mix well. Return to a rolling boil, then boil for exactly 1 minute. Remove from heat; skim off foam with a metal spoon.

Step 3

Ladle jam into hot sterilized jars, leaving ¼-inch headspace. Wipe rims clean with a damp cloth; add lids.

Step 4

Process in a boiling-water bath for 10 minutes. Transfer jars to a towel and cool completely. Check for seals and refrigerate any jam that did not seal properly.