Now, get your charcoal grill ready (you may use a gas grill, but you just don't get that same flavor). When the flame has just died out, and the coals are stacked and hot, start placing the duck breasts on the grill. Cook for about 2 1/2 to 3 minutes on each side, or until rare to medium rare. Do not overcook! Remove the breasts from the grill and let them rest for a minute. Slice them on the bias and serve.