Cover the bottom of the baking dish with 8 slices of bread. Every baking dish is different so tare your bread is necessary to cover the bottom evenly. It is alright if they go up the sides slightly.
Use the cubed ham to make the next layer.
Evenly sprinkle on the shredded cheddar cheese.
Cover the cheese with the remaining 8 slices of bread.
Beat eggs, salt, seasoning salt and pepper in a bowl. Whisk in the onion powder and milk.
Pour the eggs, salt, pepper, onion powder and milk mixture over the casserole.
Cover the baking dish and place it in the fridge overnight.
In the morning, preheat the oven to 350 degrees.
Melt 1/2 cup of butter and pour it over top of the casserole.
Crush the Cornflakes and spread an even layer over top.