From America's Test Kitchen
Chicken cordon bleu solves the problem of dry, mild-flavored chicken breasts with a flavorful stuffing of sharp, nutty melted cheese and salty sliced ham. We wanted to bring this concept to the grill, but leaky cheese can cause flare-ups as it drips from the chicken and into the coals. We wanted great grilled chicken breasts with a flavorful stuffing that stayed put.
Off the bat, we knew we wanted a strongly flavored stuffing for our chicken to stand up to the grill’s smoke. We settled on more flavorful prosciutto and fontina cheese rather than the usual deli ham and Swiss cheese. And we chose bone-in, skin-on breasts since the skin acts as a natural protector of the meat. We butterflied the breasts—cutting them horizontally nearly halfway through so the meat opened like a book. We placed prosciutto-wrapped fontina inside, folded over the breast to enclose it and tied each breast up with kitchen twine. Encasing the fontina in prosciutto rather than layering it on top, prevented the cheese from leaking. We also chose to add a simple compound butter enlivened by shallots and tarragon for additional moisture and flavor.
Cooking the stuffed breasts over a modified two-level fire allowed us to first sear the breasts over the hot coals for color and flavor, then finish cooking them over more moderate indirect heat. These boneless stuffed chicken breasts were so good, we could enjoy them straight through the grilling season.
You can serve the chicken on the bone, but we prefer to carve it off and slice it before serving.