Preheat oven to 375°F (190°C) and grease a 9x13-inch casserole dish to prevent sticking.

In a large skillet, melt butter with olive oil over medium-high heat. Add diced onions and mushrooms, cooking for 5-7 minutes until softened. Stir occasionally. Add minced garlic, salt, and pepper, cooking for another minute. Stir in flour and cook for an additional minute.

Add the Marsala (or white) wine and bring to a simmer, cooking for 2-3 minutes until it slightly thickens. Stir in fat-free half & half, then chicken broth, letting the sauce heat and thicken for 2-3 minutes.

Spread uncooked brown rice evenly in the prepared casserole dish. Evenly distribute chopped cooked chicken over the rice, then pour the mushroom and sauce mixture over the chicken and rice. Sprinkle fresh parsley on top.

Cover the casserole tightly with foil and bake for 45 minutes, or until the rice is tender and casserole is bubbly. If the rice isn't fully cooked, increase the temperature to 400°F (200°C) and continue baking until the rice is tender.

Remove the cover and sprinkle grated Parmesan cheese over the casserole. Return to the oven for an additional 5 minutes to melt and slightly brown the cheese.

Remove from the oven and let sit for a few minutes to allow the flavors to meld. Serve hot and enjoy the creamy, savory Chicken Marsala Casserole!