Heat oven to 450 degrees F and arrange the rack in the middle.
Set lamb at room temperature while oven heats up, at least 20 minutes. Combine breadcrumbs, 2 tablespoons of the oil, mint, curry, salt, and pepper in a medium bowl and stir to mix thoroughly; set aside.
Pat lamb dry with paper towels, score fat in a crosshatch pattern, and season well with additional salt and pepper. Heat 1 tablespoon of the oil in a large cast iron pan over medium-high heat. When the oil is just smoking, add the lamb, fat-side down, and brown, about 5 minutes. Transfer the lamb to a plate. Brush mustard evenly on the seared side of the lamb. Press the reserved breadcrumb mixture into the meat so that it adheres. Place lamb back into the pan and roast until the internal temperature of lamb is 135 degrees F for medium rare, about 35 to 40 minutes. Allow lamb to sit for 5 to 10 minutes before carving and serving.