Method

• 1.
  For the fondant potatoes, halve potatoes crossways. Spread the softened butter in the base of a medium saucepan. Press the potatoes into the butter, cut-side down, and season with salt flakes and freshly ground black pepper, then pour over stock. Scrunch up a piece of baking paper, then press directly over the top of the potatoes to cover. Simmer over medium heat for 35-40 minutes until all liquid is absorbed and potatoes are cooked. Remove baking paper and continue to cook until the butter browns and becomes a dark caramel colour. Remove from the heat and set aside to cool in the pan.
• 2.
  For the tarragon pesto, place the oil and nuts in a blender and whiz until smooth. Add the parsley and tarragon and whiz until smooth. Transfer to a medium bowl and, just before serving, stir in the vinegar. Season to taste.
• 3.
  Preheat oven to 210°C/190°C fan-forced.
• 4.
  Using a knife, trim excess fat and sinew from the lamb cutlets and clean the bones. Season lamb racks with salt flakes and freshly ground black pepper. Heat a large ovenproof frypan over high heat. Once pan is hot, brown the racks in batches, starting fat-side down, for 5 minutes each, turning occasionally or until golden all over. Return all lamb to pan, using bones to help stand upright, and transfer to oven to roast for 10-15 minutes for rare (this time may differ, depending on size of lamb racks). Remove from oven and rest, loosely covered, for 5 minutes before carving.
• 5.
  Meanwhile, prepare the vegetables. Bring a large saucepan of water to the boil over high heat. Add butter and sugar and season with salt flakes. Add golfball carrots and radishes and cook for 10 minutes or until just tender. Remove from water with a slotted spoon to a chopping board. Cook purple haze carrots for 1 minute, then add spigarello leaves and cook for 1 more minute until carrots are tender and leaves have wilted. Drain and transfer to a large bowl. Cut the radishes into quarters and golfball carrots in half lengthways, then add to same bowl. Drizzle with lemon oil and season with salt flakes and freshly ground black pepper. Cover to keep warm.
• 6.
  Divide fondant potatoes and vegetables between 4 serving bowls. Top with lamb and a good spoonful of tarragon pesto. Season and serve sprinkled with nasturtium leaves.