In a large bowl, combine bread crumbs, garlic, rosemary, 1 teaspoon salt and 1/4 teaspoon pepper. Toss in 2 tablespoons olive oil to moisten mixture. Set aside. Season the rack all over with salt and pepper. Heat 2 tablespoons olive oil in a large heavy oven proof skillet over high heat. Sear rack of lamb for 1 to 2 minutes on all sides. Set aside for a few minutes. Brush rack of lamb with the mustard. Roll in the bread crumb mixture until evenly coated.
For the lamb, place the lamb steak into a bowl, rub with the olive oil and season with salt and freshly ground black pepper. Heat a griddle pan and chargrill the steak for 5-6 minutes on each side, or until cooked to your liking. Leave to rest for five minutes.
If you don't have access to a grill though: Heat olive oil in a pan until nearly smoking. Sear the steak on both sides until very brown. Transfer to an oven proof pan, add your mushrooms, place a pat of butter on top of the meat and bake at 425 for about 10 minutes to finish.This would be for a steak at least an inch thick. If it's less than that, then searing in the pan is really all you'll need to do.ook it in a skillet on top of the stove on high so it will sear the juices in. Brown on each side then take out and let it rest. Then put your mushrooms in the skillet with the drippings and about a 1/2 to 1 cup of water and turn on medium heat and cook until done. Great to pour over mash potatoes or rice.