Set a frying pan with the oil over a high heat. Season the lamb rack then cook until caramelised on all sides. Transfer to a board.
Combine the mustard, garlic, oregano, olive oil and 1 tsp sea salt. Place the lamb on a baking tray and spread with the mustard mix, keeping the bones clean. Roast for 15-20 minutes, or until done to your liking.
Remove from the oven and leave to rest for 5 minutes before carving and serving.