Pat the racks of lamb dry with paper towels. Trim away all but a thin layer of fat from the meat.
Mix 1 1/2 teaspoons (9 g) of the kosher salt and 1/2 teaspoon (1 g) of the black pepper in a small bowl. Rub this mixture evenly over both racks of lamb.
Place the garlic, parsley, thyme, sage, rosemary, Dijon mustard, olive oil, the remaining 1/2 teaspoon (3 g) of salt, and the remaining 1 teaspoon (3 g) of black pepper into a food processor. Blend until it forms a thick paste.
Preheat your oven to 350°F (175°C). Move an oven rack to the middle position.
Heat the vegetable oil in a large, heavy skillet over high heat for about 2 minutes until very hot.
Sear the racks of lamb one at a time. Brown them on all sides except the flat ends, taking about 10 minutes per rack.
Transfer the seared lamb to a roasting pan. Once the meat is cool enough to handle, press the herb paste firmly onto the meaty sections.
Roast the lamb in the oven for about 20 minutes. After 12 minutes, cover the exposed bones loosely with aluminum foil so they do not burn. The USDA recommends cooking whole cuts of lamb to a safe internal temperature of 145°F (63°C).
Remove the lamb from the oven and cover it loosely with foil. Let it rest for 10 minutes before slicing into double chops.