Preheat oven to 350F. Spray the 9x13 baking dish with nonstick spray.
Spread the broccoli in the bottom of the dish.
Top with diced chicken and final the potatoes.
In a separate bowl, combine the mayo, milk, soup, and seasonings. Mix in 1 cup of the shredded cheese.
Pour over the potatoes and spread to cover.
Top with remaining shredded cheese.
Mix the melted butter and corn flakes.
Sprinkle over the top of the cheese.
Bake covered for 20 minutes.
Uncover and bake for 10 more to get the topping golden brown.
When brown and bubbly, remove from the oven and serve.