1) Preheat the oven to 180°C/Gas 4.
2) Heat half the vegetable oil in a frying pan. Season the lamb pieces and fry for five minutes until caramelised all over
3) Whilst the lamb is cooking, heat the remaining oil in a separate ovenproof casserole dish. Fry the button onions and carrots for three to four minutes until browned. Add the tomato puree and cook for a further two minutes.
4) Drain the lamb in a colander. Pour the white and Madeira wines into the frying pan, bring to the boil and scrape the sediment from the bottom of the pan. Add to the vegetables in the casserole dish.
To serve, spoon into large bowls and scatter over the chopped mint leaves.
Tip: When choosing cuts of meat for a casserole, buy something with a little fat, as this will prevent the meat from becoming too dry.