Step 1: Prepare the Onions

In a large skillet, melt the butter over medium heat. Add the thinly sliced onions, stirring occasionally, and let them cook slowly. Caramelizing onions properly takes about 15-20 minutes, but patience is key! You want them to turn golden brown and develop that rich, sweet flavor. If they start to burn, reduce the heat slightly and stir more frequently.

Step 2: Brown the Ground Beef

Once the onions are caramelized, push them to the side of the skillet and add the ground beef. Cook over medium-high heat, breaking it apart with a spoon, until it’s fully browned and no longer pink. Drain any excess grease, then stir the onions and beef together to combine their flavors.

Step 3: Add the Rice and Seasoning

Sprinkle the garlic powder, onion powder, black pepper, and salt over the beef and onions. Stir well to coat everything evenly. Next, add the uncooked long-grain white rice and stir again, allowing the rice to absorb some of the flavorful fat from the beef and onions.

Step 4: Add Liquids and Simmer

Pour in the beef broth, French onion soup, and Worcestershire sauce, stirring everything together. Bring the mixture to a gentle simmer, then reduce the heat to low. Cover the skillet with a lid and let it cook for about 20 minutes, or until the rice has fully absorbed the liquid and is tender. Avoid stirring too often to prevent the rice from becoming mushy.

Step 5: Transfer to a Baking Dish

Once the rice is cooked and the mixture is thickened, transfer everything into a lightly greased 9×13-inch baking dish. Spread it out evenly with a spatula.

Step 6: Add Cheese and Bake

Sprinkle the mozzarella and cheddar cheese evenly over the top of the casserole. Preheat your oven to 375°F (190°C) and bake uncovered for 15-20 minutes, or until the cheese is melted and bubbly. If you prefer a crispy golden top, you can switch the oven to broil for the last 2-3 minutes, but keep a close eye to prevent burning.

Step 7: Garnish and Serve

Remove the casserole from the oven and let it sit for 5 minutes to allow the flavors to settle. Sprinkle freshly chopped parsley over the top for a pop of color and freshness. Serve warm and enjoy!