Cook the white rice according to package instructions in 2 cups of water until tender. Set aside.

Heat a large skillet over medium heat. Add the diced onion and cook until translucent and sweet, about 5 minutes. Add the minced garlic and cook for another minute until fragrant.

Increase the heat slightly, add the ground beef, and break it up with a wooden spoon. Cook until browned, about 7-8 minutes. Season with salt, pepper, and oregano. Drain any excess fat.

Stir in the cream of mushroom soup, beef broth, and sour cream. Mix until well combined to create a creamy sauce.

Fold in the cooked white rice and half of the shredded cheddar cheese. Stir until everything is evenly coated. If the mixture is too thick, add a splash more broth.

Transfer the mixture to a greased 9x13 baking dish. Sprinkle the remaining cheddar cheese on top. Bake at 375°F for 20-25 minutes, until the edges are bubbling and the top is golden and crispy.

Let the casserole sit for 5 minutes before serving to allow the sauce to thicken.