Sprinkle lamb with 1 tbsp. kosher salt. In a small bowl combine harissa paste, oil, and remaining 1 tbsp. kosher salt. Preheat oven to 225°. Rub harissa mixture over the lamb thoroughly, getting between the bones and crevices. Place a wire cooling rack on a sheet tray and place lamb on rack. Place the sheet tray on the top rack of the oven and cook lamb until the center registers 128° on a meat thermometer inserted into the thickest part of the lamb, about 45 minutes.
Heat a gas or charcoal grill to medium. Place the lamb fat-side down on the grate and cook until browned, 2 to 3 minutes. Turn lamb over and cook the other side, about 2 minutes more, until internal temperature registers 133° for medium rare (for medium, cook until temperature reaches 138°). Remove the lamb and let rest 10 minutes. Slice into chops, spoon Eggplant Puree on a platter, and assemble lamb on top. Sprinkle with a little sea salt and drizzle with Chermoula.