Core, peel, and slice pears. Cook in a large pot with 1/2 cup water until soft. Process in a food mill or food processor (or just mush, which is what I did). Add, sugar, grated orange peel, nutmeg, and orange juice. Simmer slowly until mixture thickens and rounds up on a spoon. Stir frequently. Ladle hot butter into jars, leaving 1/4-inch headspace. Put on lids and bands. BWB 10 minutes.