Bring a large pot of salted water to a boil. Carefully add the whole cabbage and simmer for 5–10 minutes until tender. Remove and cool slightly, then peel off 8–10 leaves.

In a large skillet, heat a splash of vegetable broth over medium heat. Add diced onions and sauté for 3–4 minutes. Add carrots, mushrooms, and cauliflower, and cook for 5–7 minutes. Stir in minced garlic and cook for another minute.

Let the vegetable mixture cool slightly. In a large mixing bowl, combine cooked brown rice, the sautéed filling, soy sauce, vegan Worcestershire sauce, panko bread crumbs, and flax egg. Mix well.

Cut a V-shape at the base of each cabbage leaf to remove the thick stem for easier rolling. Lay each leaf flat.

Spread a bit of marinara sauce in a baking dish. Place filling on each leaf and roll tightly, arranging rolls seam-side down.

Preheat oven to 350°F (175°C). Pour remaining marinara sauce over the rolls, cover with foil, and bake for 45 minutes.

Remove foil and let cool for a few minutes. Serve warm, garnished with fresh parsley.