Place all the ingredients in a blender or food processor and pulse to combine. Place 1 Tbsp of butter in under the skin of each chicken and then rub down each chicken with the wet jerk rub. Cover with plastic wrap and allow to refrigerate for 4 hours or more.
When its time to cook, heat a large cast-iron skillet or grill pan to high heat and sear each chicken leg until slightly charred on each side. Place the dish of chicken in a preheated 375 degree oven and bake for another 20-30 minutes depending on the size of legs until the juices run clear and the chicken is cooked through.