Spray a 9x13 inch casserole dish with cooking spray. Cut each biscuit into quarters and spread on the bottom of the casserole dish.
In a small saucepan, melt 2 tablespoons butter over medium heat. Stir in flour until smooth. Slowly whisk in the milk and bring to a boil. Stir constantly until thickened, about two minutes. Remove from heat. Stir in Parmesan cheese. Spread sauce over the biscuits in the casserole dish.
Heat olive oil over medium heat in a large skillet. Brown chicken, about 7 to 9 minutes. Stir in onions, garlic and broccoli and cook until onions and broccoli are softened, about 5 minutes. Spread veggie/chicken mixture over the sauce mixture in the casserole dish.
Top veggies/chicken with shredded cheddar cheese.
Mix together 2 teaspoons melted butter and bread crumbs. Sprinkle evenly on top of cheese.
Bake, uncovered, in a preheated 400°F oven for 30 minutes, or until cheese is melted and bread crumbs are browned. Serve hot.