Remove lamb from refrigeration up to two hours prior to grilling and rest on the counter, elevating to near room temperature. 30 minutes before laying lamb to flame, preheat grill to medium-high heat.
Meanwhile, prepare both the pistachio-parmesan crust mixture and lamb racks.
In a food processor add pistachios, breadcrumbs, parmesan cheese, and parsley. Pulse together until finely mixed, then fold in 2 tablespoons butter and season to taste with salt and pepper.
Score the lamb fat cap in crosshatch-fashion, brush each rack with 1 tablespoon of butter, then generously season with salt and fresh ground pepper. Position lamb on the grill over direct heat. Sear with the grill lid open until nicely charred, approx 2-3 minutes per side. Remove lamb from heat and rest for 10-15 minutes.
Brush seared lamb with remaining butter then apply the pistachio-parmesan mixture over entirety of the lamb rack. Place lamb in a cast iron dish and set atop indirectly heated grill grates. Close the grill lid and cook until lamb has encrusted and internal temperature elevates to 125-130F. Remove lamb from heat and set aside to rest on a cutting board for 15-20 minutes.
Delicately carve the racks into chops. Plate over a bed of cous cous salad. Garnish in fresh herbs. Pair with a gorgeous cabernet. And, enjoy amongst family and friends.