Preheat the oven to about 190oC and bring the lamb to room temperature for about 20 minutes.
Brush the lamb with the oil, then fry the racks in a hot griddle pan for 2-3 minutes on one side.
Turn and brush the cooked side with some harissa paste and leave for another 2-3 minutes.
Flip and brush again and cook for another minute on each side and finally sear the ends for a minute or 2.
Transfer the racks to the preheated oven and cook to your liking (about 8-10 minutes for medium-rare), then allow to rest under some foil for around 10 minutes.