Prepare the Rice: Wash the basmati rice under cold running water until the water is clear. Next, soak the rice in a bowl of salted water for a minimum of 30 minutes, then drain thoroughly.

Bloom the Saffron: Grind the saffron with a pinch of salt in a small bowl, then add 2 ice cubes and let it sit to bloom while you prepare the rest of the dish.

Cook the Lamb: In a large pot, heat 2 tablespoons of vegetable oil over medium heat. Add the lamb pieces and sear until browned on all sides. Add the beef bone for extra flavor if using, then stir in the chopped onion and garlic. Cook for 5-6 minutes until the onions are soft.

Add Spices and Tomato Paste: Stir in the tomato paste, cinnamon stick, cinnamon powder, turmeric, black pepper, and 1 tablespoon of salt. Cook for another 2-3 minutes to let the tomato paste caramelize and the spices release their aroma.

Add Green Beans: Add the green beans to the pot, stir to combine, and cook for 3-4 minutes. Pour in about 1 cup of water, reduce the heat, and let the mixture simmer gently for 20-25 minutes, or until the lamb is tender.

Par-cook the Rice: While the lamb is simmering, bring a large pot of water to a boil and add the drained basmati rice. Cook for about 5-7 minutes until the rice is partially cooked, then drain and rinse under cold water.

Layer the Rice and Lamb: In a spacious pot, warm 2 tablespoons of vegetable oil over medium heat. Begin layering the partially cooked rice with the lamb and green bean mixture, starting and ending with a layer of rice. Pour the bloomed saffron over the top layer of rice.

Steam the Rice: Cover the pot with a lid wrapped in a clean towel to absorb moisture, reduce the heat to low, and steam the rice for 30-40 minutes. The rice should become fluffy, and the bottom layer will develop a crispy "tahdig" crust.

Serve: Once the rice is fully cooked and aromatic, carefully plate the Loobia Polo. Serve hot, with crispy tahdig on the side, for a complete Persian meal.