There are two times of the year when we seek to test our culinary mettle against friends and family: the winter holiday and grilling season. While we resort to time-honored family recipes in the winter, summer favors variety and experimentation, often in the form of handheld meals that cry out for a little something extra . . . perhaps a little hidden moisture that pushes the dish into mouth-watering territory. Forget the mayo, reach for the aioli.