Preheat the oven to 200°C/gas mark 6. Put the butternut squash in a roasting tray and drizzle with 1 tbsp of the oil. Add the garlic cloves and season well. Stir to ensure the squash is coated in the oil and roast in the oven for 25-30 minutes until soft and golden.
Meanwhile, heat the remaining olive oil in a large frying pan and fry the onion with the spices for 5-6 minutes until the onion is soft. Add the tomatoes, stock, vinegar and pomegranate molasses and simmer over a gentle heat for around 20 minutes until the tomatoes have reduced slightly. Add the roasted squash and butter beans, stir well to combine, and continue to cook for another 2-3 minutes until the beans have warmed through. Season well and stir through the parsley.
In a small bowl, mix together the Greek yogurt and harissa. Serve the stew with a dollop of the harissa yogurt on the top and the flatbread on the side.