This recipe was taken from the NY Times Cooking section. The flavor of blueberries resides almost completely in the purple skins, full of compounds called terpenes. The skins have piney, citrusy qualities, but those flavors cook off quickly, which is why blueberry pies and jams so often taste of sweet and nothing else. Adding lime juice and zest after cooking brings back the sweet-tart balance of the berries. Note: Cooking time below includes refrigeration time for gel to completely cool and set.