Preheat oven to 400 degrees F.
Remove lamb from refrigerator for at least 10 minutes. Then season generously with salt and pepper.
In a small bowl - combine mustard, honey, and tarragon. Set aside.
Heat cast iron skillet. Once hot, add grape seed oil. Brown lamb on all sides - you may need to do this one-at-a-time or in batches.
Once all browned, place all racks in pan (fat side down, rib side up). Move pan to oven and cook for 12 minutes.
Meanwhile - bring a small pot of water to a boil. Add mint leaves for 10 seconds, then move to ice water to cool down quickly. Remove from water, squeeze out water, and dry excess water with paper towels. (This step will prevent the mint from turning brown.)
In food processor, add mint, breadcrumbs, salt, pepper, cayenne, and olive oil. Pulse until fully combined and mint is finely chopped. Then add parmesan and pulse for about 15 more seconds. Transfer mixture to a plate. (These steps can be done before cooking the lamb.)
Remove lamb from oven. Then crank the oven heat to 450 degrees F.
Transfer lamb to plate and baste with mustard sauce all over, except rib side.
Roll the lamb in breadcrumbs, making sure to cover all meat areas. Use hand to pat down crumbs, if necessary. You want an even coating all over meat, but none on rib side.
Transfer lamb racks back to pan, rib side down, bread crumb side up. Cook for 12 more minutes.
Remove lamb from oven and pan. Let rest for 10 minutes.
Slice racks in half, 2 ribs per piece.
Serve and enjoy!