Cut breasts through white cartilage at V of neck.
Using both hands, grasp the small bones on either side.
Bend each side back, pushing up with fingers to snap out breastbone, keeping meat in one piece.
Do not remove skin.
Sprinkle cut side with salt.
In skillet cook onion and celery in the 2 tablespoons butter till tender.
Add corn, stuffing mix, egg, poultry seasoning, and salt; mix well.
Spoon some corn mixture on cut side of each chicken breast.
Fold over and skewer or tie closed.
Grill chicken over medium-hot coals till tender, 30 to 35 minutes, tuming;often.
Brush with the 1/4 cup melted butter during the last 10 minutes.