Heat a large 12-inch oven-safe skillet (see notes) on medium-high heat and add 2 tablespoons of butter.
Once melted, add in the minced garlic and cook another 30 seconds until fragrant.
Whisk in the flour and cook another 1-2 minutes.
Add in the half n half and whisk until combined, reduce the heat to medium and let simmer 2-3 minutes to thicken.
Whisk in the Italian seasoning, garlic powder, salt, pepper, and nutmeg until combined.
Add in the parmesan cheese until smooth.
Turn off the heat and fold in the chicken, broccoli, and shredded cheese, and set aside.
Biscuit Topping
In a large bowl add the biscuit mix along with the milk and cheddar cheese and mix until combined. Using a spoon drop about 10 scoops of biscuit on top of the chicken filling.
Bake in the center rack for 25-30 minutes or until golden brown and bubbly.
While the casserole is baking mix together the melted butter with the biscuit seasoning pkg.
Remove from the oven and brush the melted butter mixture over the biscuit. Serve!
Notes
If you dont have an oven-safe skillet, pour the filling into a 9x13 baking dish sprayed with non-stick cooking spray.