Preheat oven to 375°F (190°C). In a medium pot, bring 4 cups of the birria consommé to a boil. Stir in the rice, reduce heat to low, cover, and simmer for 15-20 minutes until the liquid is absorbed.

While the rice cooks, slice the tops off the bell peppers (about ½ inch down). Set the tops aside. Carefully remove the seeds and white membranes from the inside of each pepper. Arrange the peppers standing upright in a large, deep baking dish where they can fit snugly together. Pour the remaining 1 cup of consommé into the bottom of the dish.

In a large skillet, heat the olive oil over medium heat. Add the chopped onion (and the chopped pepper tops, if you like) and cook until soft, about 5 minutes. Stir in the minced garlic and cook for 1 minute more.

In a large bowl, combine the cooked rice, the sautéed onion and garlic mixture, the shredded birria meat, black beans and corn (if using), 2 cups of the shredded cheese, and the cumin. Mix thoroughly and season with salt and pepper to taste.

Carefully stuff each hollowed-out pepper with the birria filling, packing it in firmly. Cover the baking dish tightly with aluminum foil and bake for 40-45 minutes.

Remove the foil and sprinkle the remaining 1 cup of cheese evenly over the tops of the peppers. Bake uncovered for another 10-15 minutes, until the peppers are fork-tender and the cheese is bubbly and golden. Let stand for a few minutes before serving with optional garnishes.