Preheat the oven to 210 degrees Celsius (gas mark 6-7).

Rinse the sweet potatoes and pierce them with a small, sharp knife.

Place the sweet potatoes on a baking tray and bake for 1 to 1.5 hours, or until soft.

Heat the olive oil in a large saucepan over medium heat.

Cook the onion for about 5 minutes, stirring occasionally, until very soft and golden.

Add the garlic and spices (cumin, coriander, chili powder) and cook, stirring, for 1 minute.

Add the chopped tomatoes and vegetable stock, stir well.

Add the cubed courgette, cubed green pepper, corn kernels, and rinsed and drained red kidney beans.

Bring the mixture to a boil, then reduce the heat and simmer, partially covered, for 20 minutes.

Uncover the saucepan, increase the heat slightly, and cook for a further 10-15 minutes, or until the liquid has reduced and thickened.

Stir in the chopped fresh coriander leaves just before serving.

To serve, cut the baked sweet potatoes in half lengthwise.

Spoon the vegetable mixture over the top of the sweet potatoes.

Add a dollop of sour cream (or soy sour cream) and sprinkle with grated cheddar cheese (or soy cheddar cheese).