Heat a griddle pan, or the grill, until really hot. Brush the kebabs with a little olive oil and cook for about 10 minutes, turning often, until they are browned all over and cooked through.
Meanwhile, put the couscous in a large bowl and pour over the hot stock. Cover with clingfilm and leave for 5-10 minutes, until all the stock has been absorbed and the couscous is soft. Heat a small pan over a medium heat, add the walnuts and cook for 3 minutes, until lightly toasted. Leave to cool.
Peel the carrot, then finely chop, along with the beetroot. Fluff up the couscous with a fork, then stir through the veg, parsley, mint and walnuts, reserving a little of the herbs and some walnuts to garnish. Whisk together all the dressing ingredients, stir through the couscous and serve alongside the kebabs.
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