In a small bowl mix the glaze ingredients (hoisin sauce, lime and coriander).
Using a sharp knife score the skin of the duck breasts in a diamond pattern. Cut through the fat but not into the meat. Trim any excess skin and fat that hangs over the edges. Allow the duck to stand at room temperature for 15 to 30 minutes before grilling.
Prepare the grill for direct and indirect cooking over medium heat (350° to 450°F).
Brush the cooking grates clean. Grill the duck, skin side down, over direct medium heat, with the lid closed, for 4 minutes (if flare-ups occur, move the duck temporarily over indirect heat), then brush liberally with the glaze and turn.
Place the duck, glaze side down, over indirect medium heat. Brush the tops with glaze and grill for an additional 5 to 8 minutes. Brush with glaze once again just before removing from the grill. Keep the lid closed as often as possible during grilling. Let the duck rest for 3 to 5 minutes before cutting crosswise against the grain. Serve warm.