Preheat oven to 450 degrees. Heat an oven proof skillet large enough to hold both racks of lamb until hot over medium-high heat. If you do not have a skillet large enough for both racks then place a roasting pan in the oven to heat up as the oven does.
Season the lamb generously with salt and pepper on all sides. Heat 1 tablespoon of oil in the pan and sear the lamb on all sides for about 2 minutes per side. Let the lamb cool a little.
Put the pistachios in the bowl of a food processor and pulse a few times to grind them. Add the remaining 2 tablespoons of olive oil, the mint, garlic, and the zest and juice of the lemon. Process until it turns into a paste. Spread the paste on the meat-side of the lamb racks pressing down firmly. Place the lamb racks back in the skillet (or in a roasting pan) bone-side down. Roast for 20 minutes for medium rare, 25 minutes for medium. Cover the lamb with a piece of foil and let sit for 10 minutes before cutting the lamb into chops. Use a sharp, thin knife to carve.