Method

1. Put the racks in a dish flesh-side up and make slashes into the flesh with a sharp knife to allow the flavours to penetrate. Mix together 2 tbsp olive oil, the mustard, garlic, rosemary and parsley. Season well and rub the mixture onto the flesh to coat the lamb evenly. Cover and marinate in the fridge for 1 hour or, ideally, all day.
2. Heat the oven to 200C/fan 180C/gas 6. Put the lamb in a roasting tin and cook for 30-40 minutes depending on the size of the rack. Remove from the oven, cover with foil and rest for 10 minutes before carving into cutlets and serving on warmed plates.