Butter 2 slices of bread, cut into ½ inch cubes, remaining slices cut into 1 inch cubes. (If you are going to chill this overnight, wait on the buttered bread until just before baking.)
Place ½ the unbuttered cubes in the bottom of a 8x8 inch baking pan.
In a large mixing bowl, add the chicken, onion, celery, bell pepper, mayo, salt, and pepper. Mix to combine.
Spoon chicken mixture over the bread cubes.
Sprinkle remaining unbuttered bread cubes over the chicken mixture.
In a mixing bowl, add the eggs and milk, whisk together.
Pour egg mixture over the bread cubes.
Cover and place in the fridge to chill for at least 1 hour or even overnight.
Preheat your oven to 160° C (325° F).
Spoon soup over the bread cubes.
Bake for 50 minutes or until set.
Sprinkle with the cheese, bake for another3-5 minutes.
Serve with sides of your choice, enjoy.