In a large skillet, melt 2 tablespoons of unsalted butter over medium heat. Add 1 pound of lean ground beef, breaking it apart with a spatula. Cook for about 6-8 minutes, stirring occasionally until the beef is browned and no longer pink.

Stir in 1 teaspoon of onion powder and 1 teaspoon of garlic powder, seasoning the beef mixture with salt and pepper to taste. Sauté for another 1-2 minutes to allow the spices to bloom.

In a mixing bowl, combine the cooked beef with 2 cups of cooked white rice, 10.5 ounces of condensed French onion soup, and 1 cup of sour cream. Stir until all ingredients are well blended.

Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking dish with butter or cooking spray.

Transfer the beef and rice mixture into the greased baking dish, spreading it evenly. Sprinkle 1 to 2 cups of shredded mozzarella cheese on top.

Bake uncovered for about 25-30 minutes until the cheese is melted, bubbly, and lightly golden brown.

Once baked, carefully remove the casserole from the oven and let it cool for a few minutes. Sprinkle chopped parsley over the top before serving.