Place oil, rosemary and garlic in bowl, combine and set aside.
Rub chicken thighs with one teaspoon of olive oil and add salt and pepper to both sides.
Grill the Rosemary Garlic Chicken Thighs
Preheat your grill to 500 degrees and add the empty cast iron skillet. After about five minutes, move to the next step.
Reduce the grill temperature to 425 degrees
Place chicken thighs (skin side down) in the preheated cast iron skillet. The hot skillet will cause the skin of the chicken to immediately sear and it will trap the juices inside the meat.
In 15-20 minutes, brush the chicken with the Garlic Rosemary Olive Oil mixture. Flip the chicken over, and brush on more of the oil mixture
Continue grilling until the chicken temperature reaches 165 degrees. This should take about 10 minutes.
Very carefully remove the skillet. The skillet will be extremely hot and there will be some hot splatter.
Let it rest for 10 minutes before serving
Notes
This is an extremely simple recipe, but the key is to let the skillet heat up to 500 degrees. When you place the chicken thigh on the hot skillet, it will immediately form a hot sear and trap the liquids inside. The end result will be a crispy skin that is packed with flavor from the Garlic and Rosemary.