Remove lamb from refrigerator 30 minutes before cooking and pat completely dry. Season both racks generously with salt and pepper. Set up your charcoal grill for two-zone cooking with all coals banked on one side for a hot direct zone and a cooler indirect zone. Preheat grill grates over direct heat until they reach 500-600°F.

Drizzle olive oil over lamb racks and place fat-side down over direct heat. Sear for 3-4 minutes until deeply golden, then flip and sear the meat side for 3-4 minutes. Sear the ends for 1-2 minutes each until all surfaces are caramelized. The internal temperature should be around 80-90°F at this point.

Remove racks from grill and brush the fat cap with a thin, even layer of Dijon mustard while the lamb is still hot. In a bowl, combine Parmesan, panko, garlic, rosemary, thyme, and melted butter until the mixture resembles wet sand.

Press the Parmesan mixture firmly onto the mustard-coated fat cap of both racks, packing it down to form a ¼-inch thick cohesive crust. Make sure there are no gaps and the entire mustard layer is covered.

Adjust grill to 275°F and place lamb racks bone-side down on the indirect heat side, away from the coals. Close the lid and cook for 15-20 minutes until the internal temperature reaches 130-135°F for medium-rare (or 125°F for rare, 140°F for medium). The crust should be golden brown and crispy.

Transfer racks to a cutting board and rest uncovered for 5-10 minutes. Slice between the bones to create individual chops and serve immediately with your choice of sides.