This Chicken Broccoli Casserole is an easy, low-carb version of classic Chicken Divan, with tender white meat chicken, savory broccoli and mushrooms, and mozzarella cheese sauce.
Preheat oven to 350˚F. Lightly grease a 9x13 baking dish with cooking spray; set aside.
Heat olive oil in a large 12-inch skillet set over medium-high heat. Add mushrooms to the hot oil and cook for 2 minutes.
Stir in broccoli and garlic; season with salt, pepper, basil, and oregano, and continue to cook for 3 more minutes, or until just beginning to soften.
Shred or chop cooked chicken and arrange in baking dish.
Remove mushroom and broccoli mixture from pan and layer over the chicken. Set aside.
Set skillet back over medium-high heat. In a small mixing bowl combine 1 tablespoon chicken broth with 2 teaspoons cornstarch; whisk until pasty. Add 1 cup chicken broth to the hot skillet; to the skillet, whisk in the cornstarch paste, heavy cream, thyme, salt, pepper, half of shredded mozzarella, and parmesan cheese.
Remove from heat and pour sauce over chicken mixture inside the baking dish; using a spoon, stir and mix until thoroughly combined. Sprinkle top with remaining mozzarella cheese.
Cover baking dish with foil and bake for 15 minutes. Remove foil and continue to bake for 9 to 10 more minutes, or until cheese is melted and light golden brown on top.
Remove from oven and let stand 5 minutes. Garnish with red pepper flakes, grated parmesan cheese, and parsley. Serve.