In a bowl, whisk together the brown sugar, allspice, salt, black pepper, cumin, cinnamon, and nutmeg. Set aside.
In a food processor, blend onion, green onions, jalapeños (depending on desired heat), garlic, spices, olive oil, and soy sauce. Transfer marinade to a baking dish with chicken. Cover and marinate for 1-2 hours in the fridge.
To grill the chicken
Grill the chicken over a medium-hot fire, turning occasionally, until well browned and cooked through, 35 to 40 minutes.
To bake the chicken
Preheat oven to 375ºF. Line a baking sheet with parchment paper and spray with cooking spray. Place the chicken pieces skin-side up into the baking dish.
Bake for 40-45 minutes until fully cooked and an internal temperature reads 165ºF. Broil for the last 2 minutes before removing from the oven. Let the chicken rest for 5 minutes before serving.
Serve jerk chicken with rice, beans, and plantains. Enjoy!