Thoroughly wash the large head of green cabbage under cool running water. Remove any tough outer leaves, then cut the cabbage into quarters and chop into bite-sized pieces.

In a large skillet over medium heat, heat the olive oil. Add the ground beef or ground turkey, breaking it into small crumbles. Cook for about 4 minutes until the meat begins to brown, then add diced yellow onion. Continue cooking for another 3-4 minutes until the onion softens.

Stir in the minced garlic and cook for another 30 seconds. Drain any excess grease from the skillet.

Lightly grease the inside of a 6-quart or larger slow cooker and spread half of the chopped cabbage evenly across the bottom.

Spoon the browned meat and onion mixture over the cabbage, spreading it evenly. Rinse the uncooked long grain white rice under cold water until the water runs mostly clear.

Sprinkle the rinsed rice evenly over the meat mixture in the slow cooker, then arrange the remaining chopped cabbage over the rice.

In a large mixing bowl, combine the crushed tomatoes, diced tomatoes with their juices, and the beef broth. Add the tomato paste, Worcestershire sauce, paprika, Italian seasoning, salt, and ground black pepper. Stir in brown sugar if desired.

Whisk the tomato sauce mixture until evenly distributed, then pour it over the cabbage and meat layers in the slow cooker. Press the cabbage down gently to ensure the rice is submerged.

Secure the lid and cook on LOW for 5-7 hours or HIGH for 3-4 hours. Ensure the rice absorbs enough liquid for perfect texture.

Once done, gently stir the casserole to distribute the sauce. Allow it to rest for about 10 minutes before serving. Spoon into bowls, sprinkle with parsley, and serve warm.