Via: Martin Poole, Ellis Parrinder
Preheat the oven to 190°C/gas mark 5. Trim off any excess fat on the lamb and score the top with a sharp knife. Season with salt and pepper and sprinkle over the rosemary.
Heat a pan with the oil or butter and cook the lamb fat side down for four minutes, turning it over every minute until browned. Pop it in the oven for 15 minutes then leave it to rest for five minutes.
To make the cauliflower mash, cook the cauliflower in a pan of boiling water for 7-10 minutes until it is cooked through, then drain. Meanwhile, heat the oil or butter in a frying pan and throw in the onion. Sauté for three minutes, then throw in the garlic, rosemary and a big pinch of salt. Cook for another 3 minutes then leave to cool slightly. Mash the onion mix with the cauliflower, scraping out all the spices and oil from the pan.
Serve the mash and lamb together with a drizzle of olive oil and a pinch of chilli flakes.