Combine all ingredients (except cornstarch and water) in a heavy pot and allow to simmer until cherries and pears are tender and the mixture thickens. If you want the mixture to be thicker, combine the water and cornstarch and pour into the simmering sauce. Allow to cook for a minute. Remove from the heat and allow to cool. Store in a glass jar in the refrigerator. (This would also be delicious over ice cream!!)