Preheat the oven to 350°F (175°C).
Steam the broccoli florets until just tender, about 4-5 minutes. Drain and set aside.
In a medium saucepan, melt the butter over medium heat.
Whisk in the flour and cook for 1-2 minutes until lightly golden, stirring constantly.
Gradually whisk in the milk and chicken broth, continuing to whisk until smooth.
Cook the sauce, stirring frequently, until it thickens, about 5-7 minutes.
Remove the sauce from heat and stir in garlic powder, onion powder, salt, black pepper, paprika, 1 cup of cheddar cheese, and Parmesan cheese until melted and smooth.
In a large mixing bowl, combine the cooked chicken, steamed broccoli, and the cheese sauce. Mix well to evenly coat.
Transfer the mixture into a greased 9×13 inch baking dish and spread evenly.
In a small bowl, mix the breadcrumbs with olive oil until evenly coated.
Sprinkle the remaining 1/2 cup cheddar cheese over the casserole, then evenly distribute the breadcrumb mixture on top.
Bake uncovered in the preheated oven for 30-35 minutes, or until the top is golden brown and the casserole is bubbly.
Remove from the oven and let it rest for 5 minutes before serving.