Preheat your oven to 350°F.

In a large skillet, brown 1½ pounds of ground beef with 1 medium chopped onion until the meat is no longer pink. Drain most of the excess liquid using a spoon.

While the beef cooks, prepare the rice. Bring 1 cup of water to a boil, add 1 cup of instant brown rice, stir, reduce heat to low, cover and simmer for 5 minutes. Remove from heat, stir, cover again, and let it sit for an additional 5 minutes to allow the rice to finish absorbing the water.

In a large bowl, combine the cooked beef and onions, prepared rice, drained green beans, partly drained mushrooms, tomato sauce, and all of the grated extra-sharp cheddar cheese except for ½ cup reserved for topping. Add ½ teaspoon salt, ½ teaspoon fresh ground black pepper, ¼-½ cup hot sauce (depending on your heat preference), and ½ teaspoon garlic powder. Mix well.

Transfer the mixture to a baking dish and evenly sprinkle the reserved ½ cup of grated cheddar cheese on top.

Bake in the preheated oven at 350°F for about 20-25 minutes or until the cheese is melted, bubbly, and the edges are slightly crispy.

Remove the casserole from the oven and let it rest for about 5 minutes before serving to help it set.