To a blender add the molasses, vegetable oil, soy sauce, peeled garlic, ginger (cut into chunks, peeled), cinnamon, allspice, thyme, and nutmeg. Blend until smooth. If you want extra hot jerk chicken, add the serrano to the blender, too.

Arrange the chicken pieces in the slow cooker so that they are nestled tightly and as close to the bottom as possible. Pour about ⅔ of the spice rub over the chicken and use your hands to spread it all over the chicken pieces. Save the rest of the spice rub for later use.

Cut the onion into wedges and slice the orange and serrano. Add the onion, orange, and serrano to the slow cooker. Nestle the pieces down in and under the chicken so that they make close contact. Place the lid on the slow cooker, turn it on to high, and let it cook undisturbed for four hours.

After four hours, carefully remove the chicken and place it on a broiler pan or a baking sheet covered with foil. Tongs work best for this as the chicken will be very hot and very delicate. Spread the rest of the spice rub carefully over the surface of the chicken. Adjust the rack in your oven so that the top of the chicken is 4-5 inches below the broiler. Broil on high for about 5 minutes or until the skin is crispy and browned. Watch the chicken closely as all broilers are different.