Preheat oven to 200°C (400°F) Gas Mark 6.
Season the lamb with salt and pepper. Place in the preheated oven for ten minutes. Meanwhile make up the topping - combine the herbs, breadcrumbs, seasoning and butter and mix well.
After 10 minutes remove the lamb from the oven. Spread the mustard over the top of the lamb. Spoon on the herb and breadcrumb mixture and press well onto the lamb. Place it back in the oven and roast for another 25 minutes. Allow to sit for 5-10 minutes before carving into single cutlets.