In a large-bottomed pan add the oil and gently cook the onions and garlic. Add the cumin, coriander and chilli powder and cook for a couple of minutes.
Gradually add the mince and brown evenly. Once all the mince is browned add the purée and chopped tomatoes. Drain and rinse the kidney beans and add these too.
Bring the mixture to the boil then add the peppers. Turn down to a simmer and allow to cook for one hour.
Toss the sweet potato wedges in just enough vegetable oil to coat them, then lay them out on a baking tray and roast at 200°C/400°F/gas mark 6 until golden and crunchy.
Check the consistency of the chilli – it should be thick not watery. If it is watery, allow to cook a little longer for the liquid to reduce.