1. Combine the flaxseeds with 4 tbsp water in a small bowl, and leave to thicken.
2. Preheat the oven to 200C (180C fan).
3. In a roasting tin, add the squash with 1 tbsp olive oil, za’atar, cumin and coriander. Cover the tin with foil and roast for 30-35 mins, or until the squash is tender but still holding its shape.
4. Oil a 900g loaf tin and line it with baking parchment.
5. Heat the remaining oil in a frying pan, and fry the onion, celery and mushrooms for 10-15 mins, or until softened. Stir in the garlic and miso paste.
6. Tip the pistachios, chestnuts, breadcrumbs and parsley into a bowl, stir in the flaxseed mixture, fried veg and roasted squash. Season well.
7. Put the cranberries in a pan with the sugar and cook for 3-4 minutes, or until the sugar has dissolved and the cranberries are just starting to soften. Spoon this onto the base of the loaf tin, then leave to stand for 5 mins to set slightly.
8. Top with the nut roast mixture, firmly patting it down and smoothing it out using the back of a spoon.
9. Cover with foil and bake for 25 mins, then uncover and bake for 25 mins more. Leave to rest for 15 mins, then turn out onto a serving plate, removing the baking parchment.
10. Top with extra chopped pistachios and pomegranate seeds, then serve.