In a large bowl, combine chicken pieces with yogurt, minced garlic, grated ginger, cumin, coriander, turmeric, cayenne, and salt. Mix well to coat all pieces. Cover and marinate for at least 30 minutes, or up to 4 hours in the refrigerator.

While chicken marinates, rinse basmati rice in cold water until water runs clear, about 3-4 rinses. Drain and set aside.

Heat oil in a large, heavy-bottomed pot or Dutch oven over medium-high heat. Add sliced onions and cook, stirring frequently, until golden brown and caramelized, about 12-15 minutes.

Add marinated chicken along with all the marinade to the pot. Cook, stirring occasionally, until chicken is mostly cooked through, about 8-10 minutes.

Sprinkle garam masala over the chicken and stir to combine. Remove half the chicken mixture and set aside in a bowl.

Layer the rinsed rice over the remaining chicken in the pot. Pour chicken broth evenly over the rice. Add bay leaves, cardamom pods, cinnamon stick, and salt.

Spoon the reserved chicken mixture over the rice. Sprinkle with half the cilantro and mint. Do not stir.

Bring to a boil over high heat, then immediately reduce heat to low. Cover the pot with aluminum foil, then place the lid on top for a tight seal.

Cook on low heat for 45 minutes without lifting the lid. Remove from heat and let stand for 10 minutes before uncovering.

Remove and discard whole spices (bay leaves, cardamom pods, cinnamon stick). Gently mix the biryani, being careful not to break the rice grains.

Garnish with remaining cilantro and mint, plus raisins if using. Serve hot with yogurt or raita on the side.