10 cardamom pods, smashed
1 cinnamon stick
2″ piece fresh ginger, cut into ½-inch-thick coins and smashed
½ tsp. cumin seed
3 qt. water
4 bone-in, skin-on chicken thighs
3 tbsp. butter
2 medium onions, sliced thin (about 4 cups)
2 medium jalapeño chiles, one seeded and chopped fine, the other chopped fine with seeds
4 cloves garlic, pressed
1¼ c. basmati rice
½ tsp. saffron threads
¼ c. dried currants or raisins
2 tbsp. chopped cilantro
2 tbsp. chopped mint
1. Wrap cardamom pods, cinnamon stick, ginger, and cumin seed in small piece of cheesecloth and secure with kitchen twine. In 3 ½- to 4-quart heavy-bottomed saucepan about 8 inches in diameter (not a wide dutch oven!), bring water, spice bundle, and 1 ½ teaspoons salt to boil over medium-high heat; reduce to medium and simmer, partially covered, until spices have infused water, at least 15 minutes (but no longer than 30 minutes).
2. Meanwhile, season both sides of chicken thighs with salt and pepper and set aside. Heat butter in 12-inch nonstick skillet over medium-high heat until foaming subsides; add onions and cook, stirring frequently, until soft and dark brown about edges, 10 to 12 minutes. Add jalapeños and garlic and cook, stirring frequently, until fragrant, about 2 minutes. Transfer onion mixture to bowl, season lightly with salt, and set aside. Wipe out skillet with paper towels, return heat to medium-high, and place chicken thighs skin-side down in skillet; cook, without moving chicken, until well browned, about 5 minutes. Flip chicken and brown second side, 4 to 5 minutes longer; transfer chicken to plate and remove and discard skin. Tent with foil to keep warm.
3. If necessary, return spice-infused water to boil over high heat; stir in rice and cook 5 minutes, stirring occasionally. Drain rice through fine-mesh strainer, reserving ¾ cup cooking liquid; discard spice bundle. Transfer rice to medium bowl; stir in saffron and currants (rice will turn splotchy yellow). Spread half of rice evenly in bottom of now-empty saucepan using rubber spatula. Scatter half of onion mixture over rice, then place chicken thighs, skinned-side up, on top of onions; add any accumulated chicken juices. Evenly sprinkle with cilantro and mint, scatter remaining onions over herbs, then cover with remaining rice; pour reserved cooking liquid evenly over rice.
4. Cover saucepan and cook over medium-low heat until rice is tender and chicken is cooked through, about 30 minutes (if large amount of steam is escaping from pot, reduce heat to low). Run heatproof rubber spatula around inside rim of saucepan to loosen any affixed rice; using large serving spoon, spoon biryani into individual bowls, scooping from bottom of pot and serving 1 chicken thigh per person.