Method
Place the lamb steaks into a bowl with the rosemary, garlic and oil, and stir to ensure the steaks are evenly coated. Leave to marinate for at least ten minutes (longer if you have time).
Heat a griddle pan until very hot. Remove the lamb steaks from the marinade and season them with salt and black pepper, then place in the hot pan and griddle for two minutes on each side for medium-rare meat; cook for longer if you prefer it well done. Remove the lamb steaks from the pan and leave them to rest. Keep the griddle pan hot. Place the asparagus spears on a clean plate, then drizzle over a little olive oil and season with salt and black pepper. Turn the spears to coat them evenly, then place them in the hot griddle pan and cook for 2-3 minutes until charred and just tender.Divide the spears evenly between two plates, piling them loosely, and sit a lamb steak on the top of each pile. Top each steak with a knob of butter, then scatter over the chopped parsley and serve.