In a large bowl, combine the chicken pieces with the minced hot finger pepper, garlic, ginger, yogurt, Kashmiri chili powder, turmeric, garam masala, salt, and lemon juice. Mix well, ensuring the chicken is evenly coated. Cover and marinate for at least 1 hour, preferably overnight in the refrigerator for maximum flavor.
Rinse the basmati rice in cold water until the water runs clear to remove excess starch. Soak the rice in water for about 30 minutes, then drain.
In a heavy-bottomed skillet, heat the avocado oil over medium heat. Add the sliced red onions and sauté until they are golden brown and caramelized, about 15-20 minutes. Remove half of the onions and set aside for garnishing later.
To the remaining onions in the skillet, add the marinated chicken along with the diced tomatoes and sliced potatoes. Cook until the chicken is browned and cooked through, about 10-15 minutes. Stir occasionally to prevent sticking.
In the same pot or Dutch oven, add water to a boil. Once boiling, add the drained rice and cook until it’s about 70% done (the grains should be slightly firm). Drain the rice and set aside.
In the pot with the chicken, add the partially cooked rice on top. Sprinkle the bay leaf, star anise, cloves, green cardamom pods, black cardamom pods, cinnamon stick, cumin seeds, and fennel seeds over the rice. Drizzle melted ghee on top.
In a small bowl, soak the saffron threads in heated whole milk for a few minutes. Drizzle this saffron-infused milk over the rice layer for color and aroma.
Cover the pot tightly with a lid and cook on low heat for 25-30 minutes. This steaming process allows the flavors to meld beautifully and ensures the rice finishes cooking.
Once done, gently fluff the biryani with a fork, being careful not to break the rice grains. Garnish with the reserved fried onions, fresh mint, and cilantro. Serve hot with raita or a side salad.