Heat the olive oil in a large lidded frying or saute pan and cook the onions with a pinch of salt for 6 minutes until softened. Stir in all the spices for some kick and cook for 1 minute. Add the sweet potato to give the dish some bite.
Gently fry for 10 minutes, stirring regularly then tip in the chopped tomatoes and 1 can full of water. Crumble in the stock cube, season and gently simmer with the lid on for 45 minutes.
Check the potatoes are cooked, if not continue to simmer for another 10 minutes then tip in the black beans to add bulk. Stir everything well and cook for a further 10 minutes with the lid still on.
Meanwhile, one at a time, hold the tortilla wraps using tongs over a gas hob ring, turning and moving them constantly for 1-2 minutes, allowing them to gently char all over. Immediately cut each wrap into triangles and sit on a cooling rack to crisp up.
Serve the chilli with the tortilla triangles, lime wedges and guacamole for added freshness.