• Preheat the oven to 200oC, gas mark 6.
• Cook the potatoes and squash in boiling water for 15 minutes or until tender, drain and mash, season to taste.
• Meanwhile, place the walnuts and mushrooms in a food processor. Quarter the preserved lemon, remove the flesh and discard, adding the skin to the processor bowl. Blitz to give a coarse mince texture.
• Heat the oil in a large saucepan and fry the carrots for 6-7 minutes, add the ras el hanout and harissa and cook for 1 minute. Add in the walnut mince and cook for 1-2 minutes. Stir in the tomatoes with half a can of water, lentils and chickpeas and cook for 5 minutes, season. Transfer to a 2 litre serving dish and top with the mash. Bake for 25 minutes until golden.
• Sprinkle with extra Walnuts and chopped coriander to serve.

Cooks tip

• Any root vegetables can be mashed with the potatoes for extra colour and fibre.