01 -
Preheat oven to 175°C.
02 -
In a large skillet over medium-high heat, cook ground beef until well-browned. Drain excess fat.
03 -
If using, add chopped onion to skillet and cook 3–4 minutes until softened.
04 -
Stir in French onion soup, cream of mushroom soup, garlic powder, black pepper, and thyme. Simmer for 2–3 minutes.
05 -
Add cooked rice to the skillet and mix thoroughly until evenly combined.
06 -
Transfer the mixture to a lightly greased 33×23 cm casserole dish.
07 -
Evenly sprinkle mozzarella and cheddar cheese over the top.
08 -
Cover casserole with foil and bake for 20 minutes.
09 -
Remove foil and continue baking for an additional 10–15 minutes until casserole is bubbling and golden.
10 -
Allow to rest 5–10 minutes before serving. Garnish with parsley or green onions as desired.