Harissa Baked Aubergine & Chickpeas with Sweet Potato

Preheat the oven to 200°C / 400°F / Gas Mark 6.
Prick the sweet potatoes a few times with a sharp knife, and place them on a large baking tray in the oven.
Meanwhile, in a large bowl, mix together the harissa, olive oil and tomato purée.
Trim the aubergine and slice into rounds about 1cm thick. Peel and slice the red onion. Tip them into the bowl with the harissa.
Add in the rinsed and dried chickpeas, season well with salt & black pepper, and toss everything until thoroughly coated.
When the sweet potatoes have been in the oven for 10 minutes, add the aubergines & chickpeas to the same baking tray and return to the oven for a further 30 minutes.
When the cooking time is up, check that the potatoes are cooked through by piercing with a sharp knife - they should be soft inside. If not, give them another 5-10 minutes.
Remove everything from the oven. Split open the sweet potatoes, season and mash the flesh with a fork, then place each one on a plate.
Leave the chickpeas, onions and aubergines on the baking tray. Scatter them with chopped parsley and squeeze over the juice of the lemon. Toss to coat evenly, then divide between the plates. Top with a dollop of dairy-free yoghurt and serve.