Step 1: Prepare the Marinade - In a mixing bowl, combine the extra-virgin olive oil, minced garlic, minced rosemary, kosher salt, and black pepper. Whisk together until well combined.
Step 2: Marinate the Lamb Chops - Place the lamb porterhouse chops in a large zip-top bag or a shallow dish. Pour the marinade over the chops, ensuring each piece is well coated. Seal the bag or cover the dish, then refrigerate for at least 30 minutes, or up to 2 hours.
Step 3: Preheat the Skillet - Heat a large skillet over medium-high heat. Add a tablespoon of butter, allowing it to melt and coat the bottom of the pan.
Step 4: Sear the Lamb Chops - Remove the lamb chops from the marinade, shaking off any excess. Place them in the hot skillet, sear for about 4-5 minutes on each side for medium-rare.
Step 5: Rest and Serve - Once cooked, remove the lamb chops from the skillet and let them rest for 5 minutes before serving.