This is a quick dish to throw together but one that has lots of big, bright flavours. All the small additions are prepared first so that the mutton can be eaten whilst it is still hot, with the fresh, heady aromas of the Shawarma paste. To make this dish a little more substantial, you could serve it with steamed rice or perhaps a warm chickpea salad.
Heat the oven to 150C. Place the walnuts on a baking tray and when the oven is hot, roast for 5-7 minutes, until light golden brown. Remove and allow to cool.
Wash the radishes and finely slice into rounds, using a mandolin if you have one. Remove the outer layers of the lettuces and then carefully pull apart the leaves so that they remain intact. Remove the stalks from the chillies and finely chop into round. Remove the outer layer of the spring onions and finely chop along the length.
Mix the yoghurt and Tahini in a small bowl and set aside.
Place a medium-sized frying pan (non-stick is best) on a medium to high heat and when hot, add the mince. If using a regular pan, add a little sunflower or olive oil to the pan before adding the meat. Use a wooden spoon to break up the mince into small pieces and season with a few pinches of salt. Move the meat around every minute or so. It will release water, which will eventually evaporate and then, after this, it will start to crisp up. Aim for the mince to be completely cooked with a mixture of more and less crisp parts, this should take around 5-7 minutes. Add the Shawarma paste and use the spoon to mix through and coat well. Turn the heat to low, then hand crush the walnuts into small pieces, add to the pan and mix well. Taste and add more salt if necessary. Add the spring onions and chopped herbs and mix through.
Divide the mince between lettuce leaves and then place the radish and chilli on top and serve with a squeeze of lemon and tahini yoghurt to taste.