To the hot pan, add in 4 tablespoons of the the olive oil, along with the lamb and garlic. Sear all sides of the lamb until browned, about 3-4 minutes. Remove browned lamb, and place cooked lamb onto a baking sheet.
Remove garlic and add to food processor with along with the breadcrumbs, parsley, parmesan, rosemary, and 1 tablespoon of olive oil. Pulse until combined. Pour onto a large plate.
Brush the top and sides of the lamb with mustard.
Coat the top and sides of the lamb with the breadcrumb mixture and roast in oven for 20-25 minutes.