Heat your oven to 200°C/Fan 180°C/Gas 6. Peel the sweet potatoes. Slice into wedges, around six per potato. Pop them in a bowl or dish. Drizzle with 1 tbsp olive oil.
Measure out 2 tsp of the Cajun spice mix. Sprinkle over the potatoes. Turn to coat. Spread the potatoes out on a baking tray. Bake for 40 mins till golden and tender. Turn once, halfway through cooking, to ensure they cook evenly.
Peel and finely chop the onion. Halve the chilli and finely slice it – flick out the seeds and white bits if you want a milder flavour. Peel and crush the garlic clove.
Warm ½ tbsp oil in a pan over a medium heat. Add the onion. Season with salt and pepper. Fry for around 5 mins till the onion is soft and glossy looking. Stir often while it cooks.
Stir the chilli and garlic into the onion. Measure out 1 tsp ground cumin and add that too. Fry for 1 min. Stir till the pan smells aromatic. Pour in the chopped tomatoes. Half fill the empty tomato tin with water. Add that too.
Drain the kidney beans. Rinse them. Add to the pan with a sprig of thyme. Give everything a good stir. Pop on the lid. Simmer over a medium heat for 15 mins till the chilli is thick. Stir every so often while it cooks.
While the chilli cooks, rinse the spinach. Chop off any large stalks. Finely slice the leaves. When the chilli is thick, pick out the thyme sprig and stir in the spinach till it wilts.
Taste the chilli and adjust the seasoning if you think it needs it. Serve with the sweet potato wedges and the yogurt, sprinkled with a pinch more of the Cajun spices.