Preheat oven to 375°F (190°C). Grease a 9x13 inch baking dish.
In a large bowl, combine the cooked chicken, broccoli florets, cream cheese, heavy cream, shredded cheddar cheese, sour cream, minced garlic, salt, and pepper. Mix well until everything is evenly distributed.
Pour the mixture into the prepared baking dish and spread it out evenly.
Bake for 25-30 minutes, or until the casserole is heated through and bubbly. If desired, you can sprinkle a little more cheese on top during the last 5 minutes of baking.
Let it rest for a few minutes before serving.
Notes
This casserole is also delicious topped with some crispy bacon bits before serving.