Preheat the oven: Preheat your oven to 350°F (175°C). Grease a baking dish (9×9 or similar) with olive oil or butter.
Prepare the broccoli: Steam or blanch the broccoli florets until tender. Set them aside to cool slightly.
Make the creamy sauce: In a medium saucepan, melt the cream cheese over low heat. Add the heavy cream, garlic powder, onion powder, salt, and pepper. Stir continuously until everything is well combined and smooth.
Assemble the casserole: In a large mixing bowl, combine the cooked chicken, steamed broccoli, and 1 cup of shredded cheddar cheese. Pour the creamy sauce over the mixture and toss to combine.
Bake the casserole: Transfer the mixture to the prepared baking dish. Sprinkle the remaining ½ cup of cheddar cheese (and mozzarella cheese, if using) on top.
Bake: Place the casserole in the oven and bake for about 20-25 minutes, until the cheese is bubbly and golden on top.
Serve: Let it cool slightly before serving. Enjoy this keto-friendly, cheesy goodness!