Rinse chicken inside and out under cold running water then blot dry inside
and out with paper towels.
Place the chicken on its breast. Using poultry shears and starting on the
neck end, cut out the backbone, making one lengthwise cut on either side. Remove
and discard backbone. Remove breastbone. Cut off the wing tips and trim any
loose skin. Pull down on legs to lay them flat. Season chicken generously on
both sides with salt and pepper. Paint both sides with mustard.
Place bread crumbs, tarragon, garlic and hot red pepper flakes in a large
shallow bowl or baking dish and stir to mix the chicken skin side down in the
crumbs, then turn it over and do the same on the bone side.
When ready to cook, brush and oil the grill grate. Place the chicken, skin
side up in the center of the hot grate, over the drip pan and away from the
heat. Drizzle butter over the top of chicken. Cover the grill and cook the chicken
until the crust is a golden brown and the meat is cooked through, about 40 minutes.
If the crust starts to brown too much, loosely tent the bird with the aluminum
bird with aluminum foil.