First, prepare the tagine. Heat the oil in a deep heavy-based frying pan with a lid over a low–medium heat, add the onion and fry for 4–6 minutes until softened but not coloured.
Add the garlic, ginger and pepper and cook for 2–3 minutes, then add the spices and cook for a further 2–3 minutes, stirring, until fragrant.
Add the squash and sweet potato and stir well to coat in the spices. Pour in the stock, add the sultanas and season generously.
Increase the heat to medium and bring to the boil, then cover the pan with the lid and simmer for 20 minutes or until the squash is tender. Stir through half of the coriander.
Meanwhile, make the couscous. Place the couscous in a bowl and pour over the hot vegetable stock or boiling water. Cover and leave for 5–10 minutes until all the liquid has been absorbed.
Fluff the couscous with a fork to separate the grains and let cool a little before stirring through the lemon juice, pistachios and fresh herbs. Season to taste and add a little extra-virgin olive oil, if needed.
Remove the lid from the tagine and scatter over the spinach leaves, cover and leave to wilt for 1 minute before stirring through.
Serve the tagine in warmed bowls with the couscous on the side, sprinkling both with the remaining coriander.
