1.In a shallow dish, combine the garlic, mustard, 3 tablespoons olive oil, thyme, rosemary, and ½ teaspoon each of salt and pepper.
2.Add the lamb chops and massage the mixture into both sides of each chop. Cover and marinate in the refrigerator for a minimum of one hour and up to 8 hours. Try to flip the chops halfway to ensure even flavor throughout.
3.A half hour prior to cooking, let the chops sit out at room temperature for 15 minutes. Preheat the oven to 425℉. Pat the chops dry with a paper towel, then season both sides of each chop with salt and pepper.
4.Preheat a cast iron skillet over medium high heat. Add the butter and remaining tablespoon of olive oil. Sear the lamb chops for exactly two minutes on each side. Use a spoon to baste the chops with the butter and oil from the pan once you flip them.
5.Transfer the hot skillet to the oven and continue cooking for 4-6 minutes for medium rare or a thermometer inserted into the center reads 135℉. Remove from the oven.
6.Cover loosely with foil and let the chops rest for 5-10 minutes before serving hot.