Remove damaged outer leaves from the cabbage and cut into quarters. Remove the core and chop into bite-sized pieces. Rinse and drain.

Finely dice the yellow onion and mince the garlic. Heat olive oil in a skillet and cook the ground beef until browned.

Add the diced onion to the beef, cooking until soft. Add garlic and drain excess grease.

Mix in tomato paste, spices, and seasonings, stirring for 1 minute.

Grease slow cooker, layer one-third chopped cabbage, half seasoned beef, and half rice.

Repeat layering with another one-third of cabbage, remaining beef, and rice. Top with last third of cabbage.

Combine tomatoes, sauce, broth, Worcestershire sauce, and brown sugar in a bowl. Whisk until smooth.

Pour sauce over layers, pressing cabbage down to ensure rice is submerged. Cover slow cooker.

Cook on LOW for 5-6 hours or HIGH for 3-4 hours, undisturbed.

Check for doneness. Add broth if too thick and cook until rice is tender.

Let casserole rest for 10 minutes after cooking. Stir gently to mix ingredients.

Garnish with parsley and optional green onions. Serve warm.