Wash pears; slice without removing peels or cores; place in a heavy kettle with just enough water to cover bottom.

Cook until very soft; force through a sieve to remove skins and seeds. Measure and add half as much sugar as pulp. Add spices if desired (cinnamon, allspice and/or nutmeg, clove) to taste.

Cook, stirring frequently, until smooth and thick enough to spread. Pour immediately into hot sterilized jars and seal at once.