Preheat your oven to 400°F (204°C) and bring a large pot of salted water to a boil to blanch the cabbage leaves.

In a large bowl, combine the ground beef, ground pork, parboiled rice, minced onion, garlic, salt, black pepper, dried thyme, and dried sage. Mix thoroughly to combine all ingredients evenly.

In a medium bowl, whisk together the tomato sauce and chicken broth until well blended. Set this sauce mixture aside for later.

Remove any wilted or loose outer leaves from the cabbage. Carefully separate as many outer leaves as possible without tearing them. Submerge these leaves in the boiling water for about 3 minutes until tender, then remove with tongs and drain on a plate or cutting board.

Place the whole cabbage head into the boiling water and cook for 3-4 minutes. Remove and gently peel off the softened outer leaves using tongs. Repeat this boiling and peeling process until the remaining leaves become too small or crinkled to use.

Once the cabbage leaves are cool enough to handle, use a sharp knife to trim out the thick center stem sections with a V-shaped cut to make rolling easier.

Lay each cabbage leaf flat. For leaves with trimmed stems, slightly overlap the cut parts to seal. Spoon about 3 tablespoons of the meat and rice mixture onto each leaf. Fold in the sides and roll tightly, sealing the edge over the filling. Use two leaves for larger rolls as needed.

Drizzle olive oil into a 9×13-inch baking dish or casserole pan. Place the cabbage rolls seam-side down in the pan, packing them snugly.

Pour the tomato sauce and chicken broth mixture evenly over the cabbage rolls, covering them. Tightly cover the pan with aluminum foil to trap steam and prevent drying during baking.

Bake in the preheated oven for 1 hour. Then, carefully vent the foil to release steam and continue baking for an additional 20-30 minutes until the meat is fully cooked and the internal temperature reaches 160°F (71°C).

Remove from oven and let cool slightly before serving. Garnish with freshly chopped parsley if desired.