Heat the grill. I use an indoor panini maker
Mix the chicken, with the hot sauce, mayonnaise, celery, onion, 1/4 cup of blue cheese, mozzarella cheese and cheddar cheese. If you prefer add salt and pepper to taste, but it's not necessary.
Butter each slice of bread and top with a tbsp of blue cheese on 3 of the slices.
Divide the chicken mixture in 3 and top 3 of the slices of the chicken mixture and next the other slice of bread.
Grill the sandwiches for 2 to 4 minutes, until golden brown and cheese has melted.