Combine oil and spices, then coat the chicken evenly. Let it sit at least 15 minutes, or longer for deeper flavor. Longer marination results in juicier, more flavorful chicken.
Preheat oven and place chicken on a baking sheet. Roast until cooked through and skin becomes golden and slightly crisp. Rest chicken briefly so juices redistribute before serving.
Cook onion and garlic in butter until fragrant and soft. Add rice and toast lightly before pouring in broth. Simmer with vegetables until rice absorbs liquid and becomes fluffy.
Add cilantro, jalapeños, garlic, mayo, yogurt, lime juice, and oil to blender. Blend until completely smooth and creamy. Taste and adjust salt or spice level as needed.
Place fluffy rice on serving plates or a large platter. Top with roasted chicken pieces and drizzle green sauce generously. Serve extra sauce on the side for dipping or extra flavor.