Preheat oven to 400°F (200°C). Let the lamb sit at room temperature for 30 minutes. Season generously with salt and pepper.
Heat oil in an oven-proof skillet over high heat. Sear the lamb, fat-side down, for 2-3 minutes until golden brown. Sear on all sides. Remove from heat.
Brush the top (fat-side) of the rack with Dijon mustard.
In a bowl, combine garlic, rosemary, thyme, and breadcrumbs. Press the herb mixture firmly onto the mustard-coated side of the lamb.
Place the skillet in the oven and roast for 15-20 minutes for medium-rare (internal temp of 135°F / 57°C).
Remove from oven, tent with foil, and let rest for 10 minutes. Carve between the bones and serve.
Notes
Letting the lamb rest after cooking is crucial for juicy, tender meat. Use a meat thermometer to achieve the perfect doneness. Ask your butcher to 'french' the rack for you.