Heat oven to 200°c. Spread walnuts out on a tray and bake for 5 – 10 minutes, until they start to brown and smell toasty. Take out of the oven and leave to cool.
Wash the kale and remove the stalks. Finely slice and place in a large bowl with the juice of half a lemon. Gently massage the kale with your fingers to really coat it in the juice, and leave covered for about 30 minutes.
In the meantime, finely slice the purple cabbage and the apple (I use a mandoline for the apple). Once the kale has finished marinating, throw the cabbage and the apple in, and mix to combine.
Prepare the dressing by whisking together the yoghurt, lemon juice, mustard, honey, sesame oil and salt.
Pour the dressing over the salad and mix to thoroughly combine. Leave for an hour before eating to let the kale and cabbage soften. Before serving, top with the toasted walnuts.
Notes: both kale and cabbage are pretty hearty, so this salad will stand up pretty well for two or three days in the fridge, although I’d recommend dressing it on the morning that you plan to eat it. It is also excellent with a poached egg on top if you’re looking for a bit of protein!