Position a rack in top third of the oven and heat the broiler to high. Line a rimmed baking sheet with foil. Brush the lamb racks all over with 3 Tbs. of the oil, and season all over with 1-1/2 tsp. salt and ½ tsp. pepper.

Broil the racks, meat side down, until beginning to brown in places, about 4 minutes. Flip the racks and broil until the meat begins to brown in places, about 3 minutes more. Remove the lamb from the oven and set aside to cool for about 20 minutes. Heat the oven to 450°F, and reposition the rack in the center of the oven.

Meanwhile, combine the panko, cheese, herbs, granulated garlic, ½ tsp. salt, and ½ tsp. pepper in a pie plate or rimmed plate. Add the remaining ¼ cup olive oil and mix until well combined and the mixture mostly holds together when squeezed. In a small bowl, combine the mustard with the honey and mix well. When the lamb is cool to the touch, divide the mustard mixture between the lamb racks and pat evenly over the top. Divide the breadcrumb mixture in half and press into the mustard mixture.

Return to the oven and roast until the panko coating begins to brown and the meat registers 120°F for rare or 130°F for medium rare on an instant-read thermometer, turning the pan halfway through roasting time, 20 to 25 minutes. If the panko coating begins to get too dark, cover lightly with foil. Let the racks rest for at least 10 minutes before cutting them into chops and serving.