Preheat oven to 350 degrees F. Lightly spray a 9×13 pan with nonstick cooking spray.
Place the broccoli in a saucepan with enough water to cover. Bring to a boil, and cook for about 4-5 minutes, or until tender. Drain, set aside until ready to use.
Next, season chopped chicken with salt, Creole seasoning (salt free). Thoroughly mix.
Heat oil in a large skillet, stir in the chicken, cook the chicken for about 5–6 minutes, or until cooked. Set aside.
Add butter into the skillet, let it melt, followed by minced garlic and onions ; cook until onions wilted – about 3-4 more minutes.
Stir in flour cook for about a minute to get rid of the flour taste.
Slowly add milk and chicken stock a little at the time; you do not want the mixture to form any lumps. Simmer for about 5 minutes or until mixture thickens slightly. Add creole seasoning, continue cooking for about 2 minutes.
Stir in the cheeses, Worcestershire sauce and stirring until everything’s melted and evenly combined and smooth. Sprinkle with salt & pepper and a pinch of nutmeg to taste.
Add cooked broccoli into the prepared baking dish or casserole , together with the chicken, followed by sauce.
Top with bread crumbs mixture.
Bake in the preheated oven for 18-20 minutes, or until bubbly and lightly brown.