Preheat the oven to 400°F / 204°C. Arrange a roasting pan with a rack and set aside.
Finely mince the garlic cloves, fresh rosemary, and fresh thyme. Add the garlic and fresh herbs along with the panko breadcrumbs to a small bowl and stir to combine. Season with ½ tsp kosher salt and a big pinch of pepper. Drizzle with 2 tbsp of the olive oil and stir until all the crumbs are coated.
In a small bowl stir together the Dijon mustard, ½ tbsp olive oil, ½ tsp kosher salt and a big pinch of pepper. Place the two racks of lamb in the roasting pan with the racks facing each other in the middle.
Brush the Dijon mustard mixture over the top and sides of the meaty part of the lamb. Press the herbed crumbs evenly over the lamb.
Roast for 20 to 25 minutes to an internal temp of 130° to 135°F for medium rare, or longer if desired. Check the temperature by inserting the probe into the middle of the loin at an angle. Avoid touching the bone while taking the temperature.
When done, take the lamb out of the oven and let rest for 10 to 15 minutes. Tent the lamb with a piece of foil while resting.
To carve the lamb, place the rack on a cutting board with the rack side down. Hold onto the bones to stabilize the rack. Using a sharp chef's knife, slice down in long smooth strokes between the bones at a sharp angle. Follow the angle of the individual bones. If you encounter bone at the bottom, press firmly down with the chef's knife to cut through the bone.
Transfer the lamb to a serving platter. If a lot of breadcrumbs have fallen off then scoop them up and sprinkle them over the lamb. Serve and enjoy!
Notes
*To substitute dried rosemary and thyme use 1 tsp of dried leaves or 1/2 tsp if the herbs are finely ground.