Trim fat from lamb. Season with salt and pepper. Preheat oven to 200°C (approximately 400°F) and roast lamb on a baking sheet for about 15 minutes.
Peel garlic and press. Rinse chile pepper, cut lengthwise, remove seeds and ribs and chop. Separate egg. Mix parsley with thyme, rosemary and pressed garlic. Add oil, mustard and grained mustard. Stir in breadcrumbs and egg white. Spread over lamb and roast for another 15 minutes.
Turn oven off and let lamb rest for 10 minutes. Carefully remove and serve on a bed of lettuce if desired.