1. Preheat the oven to 200°C/fan180°C/gas 6. Put 2 tablespoons of the oil in a large roasting tin and heat in the oven for 5 minutes, until smoking hot. Carefully add the potatoes, season well and toss in the oil. Roast for 20 minutes. Add the cumin and garlic to the pan, shake about and roast for a further 15 minutes or until the potatoes are cooked, crisp and golden.
2. Meanwhile, heat the remaining oil in a large frying pan over a medium heat. Add the onion, celery, pepper and chilli and cook, stirring occasionally, for 10 minutes, until soft. Add the paprika and tomato purée and cook, stirring, for a further 5 minutes. Add the chickpeas and crème fraîche and warm through for a few minutes. Stir in the spinach, until wilted. Season to taste and stir in the thyme.
3. Divide the spiced chickpeas between bowls or plates and serve with the cumin potatoes.