Preheat the oven to 200°C/400°F/gas mark 6.
Scrub the sweet potatoes under cold water and cut each into 6 wedges. Tip into a roasting tin, drizzle with 2 tablespoons of olive oil, season with salt and freshly ground black pepper, and roast in the oven for about 20–25 minutes or until the sweet potato is tender and starting to caramelise at the edges. Add the pumpkin seeds to the pan for the last 5 minutes of cooking time.
While the sweet potato is cooking prepare the couscous. Heat 2 tablespoons olive oil in a large sauté pan, add the couscous and cook gently for 2–3 minutes until starting to brown. Add half of the stock or water to the pan and continue to cook for about 15 minutes, stirring frequently until the couscous is tender and has absorbed the liquid. Add the remaining stock or water to the pan as and when needed. Add the raisins, za’tar and chopped pistachios to the pan, season with salt and freshly ground black pepper and cool slightly.
Mix together the juice from half the lemon and the extra virgin olive oil and pour over the warm sweet potato when it comes out of the oven. Gently stir the freshly chopped herbs and roasted sweet potato wedges into the couscous and serve with extra lemon wedges for squeezing over.