Balsamic Blueberry Grilled Cheese

This Balsamic Blueberry Grilled Cheese Sandwich is almost too pretty to eat—almost. Frozen blueberries are reduced along with sugar and vinegar to create a jam-like spread that might warrant a bib to prevent stains but is totally worth it. (Actually, frozen fruits are one of the Packaged Foods That Are Surprisingly Healthy.) Get your greens in with a generous handful of baby spinach or arugula for a bite that's bursting with flavor.