Whizz the breadcrumbs, parsley, rosemary and garlic together in a blender.
Spread the mustard over the lamb and then top with the crumb mixture. Leave to marinate for 30 minutes, or up to 1 hour if you have time.
Preheat the oven to 200°C, fan 180°C, gas mark 6. Transfer the lamb to a baking tray or shallow roasting tin.
Bake in the preheated oven for 20 minutes for rare lamb or, if you prefer the lamb more well-done, refer to the back of pack instructions.
To make a full meal, serve with grilled sundream tomatoes and a pack of buttery mashed potato, cooked following pack instructions.
Cook's tip: This easy meal is ideal for a special Valentine's day dinner - you could even make the crumb mixture in advance so there is minimal assembly to do on the day.