01 -
Preheat the oven to 175°C.
02 -
Heat a large skillet over medium-high and cook the ground beef until browned, breaking it apart as it cooks. Drain excess fat.
03 -
If using, add chopped onion to the skillet and sauté for 3–4 minutes until softened.
04 -
Stir in French onion soup, cream of mushroom soup, garlic powder, black pepper, and dried thyme. Allow to simmer for 2–3 minutes.
05 -
Add cooked rice to the skillet and mix thoroughly to combine all components.
06 -
Transfer the mixture into a greased 33x23 cm casserole dish, spreading evenly.
07 -
Evenly distribute mozzarella and cheddar cheese over the surface.
08 -
Cover the dish with foil and bake for 20 minutes.
09 -
Remove the foil and continue baking for 10–15 minutes until the cheese is bubbling and golden brown.
10 -
Allow the casserole to rest for 5–10 minutes before slicing. Garnish with chopped parsley or green onions, if desired.