Place the frozen turkey breast in the refrigerator 1-2 days before the cook day to defrost.
Carefully remove the skin from the turkey, and if using a bone-in breast, trim off any rib pieces that might be sticking out.
Coat the entire turkey breast with yellow mustard and season with the all purpose rub and black pepper.
Set the seasoned turkey breast aside and let it sweat and start absorbing the seasoning.
Preheat the grill to 275 degrees and set for indirect heat. Add a few wood chunks for some extra smokey flavor.
Place the turkey breast side up directly on the grates and smoke until the internal temp of the protein reaches 130 degrees. Total time 1.5-2 hours.
Place the smoked turkey breast of a sheet of aluminum foil. Pour the butter over the smoked turkey breast, wrap it tightly and place it back on the grill. Cook for another hour or until the internal temperature reaches 160 degrees.
Remove it from the grill and let it rest for 10 minutes while still in the foil.