Remove any tough stems from the kale, and chop the leaves.

Heat the oil in a frying pan, and add the minced garlic, chopped kale, and chilli powder (if using). Cook over a medium heat for a few minutes, stirring regularly, until the garlic is soft and fragrant and the kale has softened slightly. Season generously and add the black beans. Cook for another couple of minutes until the black beans are warm (alternatively, if you're serving your wraps cold, just add the beans and set aside).

Roughly mash the avocado, and spread it over the tortillas. Add the kale mixture, and roll the tortillas, tucking in one or both ends to seal.

Serve warm or cold.