For our version of shepherd's pie,we slow-cook a lamb shoulder,shred it then bake it with potato mash on top. It's dead easy but does need a small amount of planning to cook the lamb overnight. We served it here with roasted carrots but beans,broccoli,brussels sprouts or cauliflower are good too. Ask your butcher for a lamb shoulder with the bone in as it will have more flavour than the boneless version,and the natural gelatin from the bones thickens the sauce.