Combine the cashews, 2 tablespoons cilantro, oil, garlic, soy sauce, brown sugar, jalapeño, and water in s blender or food processor and blend until smooth, scraping down the sides, as necessary. Taste and season with the salt and pepper.
Season chicken all over with salt and pepper. Set aside 1/3 of the cashew mixture. Smear on enough of the remaining mixture to thoroughly coat the chicken. Let marinate at room temperature while you heat a broiler or grill. (Or refrigerate up to 12 hours before cooking.)
Broil or grill the chicken 20-30 minutes, turning frequently, until it’s crisp and golden on the outside and done on the inside. (Faith cuts into it to be sure.)
Sprinkle the chicken with the remaining cilantro and serve with lime wedges and the remaining cashew mixture. (Faith likes this with rice or quinoa when she’s feeding a crowd.)