1. Preheat the oven to 200oC/Fan 180oC/400oC/Gas Mark 6. Place the racks in a large roasting tin.
  2. Place the bread and garlic in a food processor and blend until the bread forms fine crumbs. Add the herbs and oil and blend again until roughly chopped. Lastly add the pinenuts and blend briefly until lightly chopped. The mixture should stick together lightly.
  3. Spread the mustard over the lamb rack, then press the herb crust onto each one, pressing it down firmly so it sticks. Roast for 25mins in the centre of the oven. This gives medium cooked lamb – for more well done cook for a further 10 mins.
  4. Meanwhile, make the pea puree: melt the butter in a medium pan, add the leek and saute for 3-4mins or until soft. Add the peas, mint and stock, bring to the boil, cover and simmer for 4 mins. Use a stick blender to whizz the peas mixture to form a rough puree. Add the cream and nutmeg and season to taste.
  5. Remove the lamb from the oven and leave to rest for 5 mins.
  6. To serve: carve the lamb into cutlets. Divide the pea puree between four warm plates, top with the lamb cutlets. To garnish, drizzle a little olive oil on each plate and add a sprig of mint.