Preheat grill to medium low heat
Butter fly your chicken, by cutting it horizontally. Do not cut all the way through.
Sprinkle the inside of the chicken with pepper. Evenly top the the chicken with cheese and fold over the chicken to close it. It should look like the chicken breast before you cut it.
In a microwave safe bowl (I used a pyrex measuring cup) melt the butter for 8 seconds. Stir in hot sauce and celery salt.
Brush one side of the chicken with hot sauce mixture and place the hot sauce size down on the grill.
Brush more hot sauce over top of chicken. Cook for about 7 minutes. Flip the chicken and brush on remaining hot sauce and cook until no longer pink; about 5 minutes more.
Serve with a side salad, celery, carrots and ranch dressing if desired.