Preheat the oven to 200oC/Gas Mark 6.
Pierce the sweet potatoes, and bake in the oven on a roasting tray for 40 minutes.
After 20 minutes, prepare the stuffing. Place a large pan over a medium heat and add the oil, curry powder, chilli powder and salt. Stir together for about 1 minute.
Slice the courgette and add it to the stuffing mixture. Fry for 2-3 minutes.
Add the chopped tomatoes, black beans and agave nectar. Stir everything together until well mixed, then allow the sauce to simmer for 15 minutes, stirring occasionally so that the sauce can thicken and allow the flavours to develop.
When the potatoes have cooked, remove them from the oven, then slice down the middle. Remove the stuffing mixture from the pan and spoon half of it onto the middle of each potato. Press the sweet potatoes together to hold the stuffing, then return to the oven for 5-10 minutes before serving.