Method:
1 Preheat oven 200°C fan-forced. 
2 Place lamb rack on a baking paper-lined oven tray and season with salt and pepper, drizzle with olive oil. Roast in oven for 12-14 minutes, for medium rare or until cooked to your liking. Cover loosely with foil and set aside to rest for 5 minutes.
3 Place potatoes in a microwave safe bowl, cover with a piece of damp paper towel, microwave on High/100% for 6-8 minutes or until tender, then press through a ricer into a bowl or mash until smooth. 
4 Heat oil in a saucepan over medium heat add potato, cream and chestnuts and cook for 2-3 minutes or until warmed through. Season to taste with salt and pepper.
5 Spoon creamed potato and chestnut onto a plate, top with rack of lamb and chives to serve.