For the filling, add the oil to a pan and cook the onion, chilli and garlic until softened. Add the beans and cook for a further 10 minutes, stirring occasionally. Add a little vegetable stock, about half a small glass, cook the beans until the mixture is smooth and not runny.
Mash the beans roughly with the back of a fork or a potato masher, then set aside.
For the salsa, mix together the tomatoes, red onion, a squeeze of lime juice and a handful of the chopped fresh coriander.
Just before you are ready to eat, add the remaining coriander and a squeeze of lime juice to the beans.
Warm each tortilla through in a pan and put on a plate, spoon over some of the filling, add a spoonful of the yoghurt and a little salsa. Roll up and serve immediately.