Using a mini processor or grinder, grind cinnamon hearts until powdery (some bits will remain). In a small sauce pan bring 1/3 cup water to a simmer. Whisk in cinnamon heart powder all at once, stirring constantly until starting to dissolve. Increase heat and continue to stir, melting the candy, approximately 1-2 minutes (some bits will not dissolve). Dissolve cornstarch in 2 tbsp cold water and add to liquid candy, stirring constantly. Allow to boil briefly and remove from heat. Strain while hot, removing any candy bits that refuse to dissolve. Allow to cool, stirring occasionally. Refrigerate until ready to use. Makes about 1 cup.