Add the scallions, Scotch bonnet, garlic, lime juice, soy sauce, brown sugar, oil, vinegar, thyme, allspice, ginger, black pepper, cinnamon, and nutmeg to a blender or food processor.
Blend until mostly smooth, scraping down the sides as needed.
Marinate the chicken:
Pat the chicken dry and season it with the kosher salt.
Rub the jerk marinade all over the chicken, getting some under the skin if possible.
Cover and refrigerate for at least 2 hours, or overnight for deeper flavor.
Cook and serve:
Heat a grill to medium. Grill the chicken over indirect heat for 30 to 35 minutes, turning occasionally, until the thickest pieces reach 165°F.
Move the chicken over direct heat for the last few minutes to char the edges. If roasting, bake at 425°F on a rimmed sheet pan for 35 to 40 minutes, then broil briefly for char.
Rest for 5 minutes, then serve with lime wedges, rice and peas, and extra jerk sauce if you like.
Notes
Scotch bonnet peppers vary in heat. Start with one pepper if you are unsure.
For a milder version, remove the seeds and inner ribs from the pepper before blending.
The marinade also works well with boneless chicken thighs, but they cook faster.