Preheat the oven to 350 F. Brown the ground beef with the chopped onions until there is no pink left in the meat. Season with salt and pepper and set aside.
In a large bowl, mix together the chopped cabbage, rice and tomato sauce. Season with salt and pepper.
Place half the cabbage mixture into a 9 x 13 inch casserole dish.
Spoon the meat mixture on top of the cabbage.
Top the meat with the remaining half of the cabbage mixture and pour the beef broth evenly over the casserole. Sprinkle with fresh thyme and add the bay leaves. Cover with foil and bake for 1 hour and 20 mins. Midway through the cooking time, remove the casserole from the oven, give it a little mix with a fork, cover again and continue baking.