Heat oil in large wok, add the beef breaking it down cooking for 5 minutes and then drain on paper towels.
Lower heat add remaining oil and add onions and garlic cook until soft. Add the spices and cook for another minute. Return the beef to the pan stir well and cook for 2 more minutes.
Turn off heat and add mint and walnuts.
Lay lettuce leaf, add mince and top with the yoghurt. Roll the edges in so you can eat as a wrap.