Heat the oil in a large pan on medium heat. Add the sliced onion and soften for 5-6 minutes, stirring occasionally.
Once the onions are soft, add the garlic, chilli, and green pepper. Stir well and cook for 2-3 minutes until the peppers start to soften.
Next, add the chopped jackfruit, black beans, tomato puree, vegan stock, cumin, smoked paprika, sage, nutritional yeast, salt, and pepper. Stir everything well and cover with a lid. Reduce the heat and simmer for around 6-8 minutes.
After 6-8 minutes, remove the lid. Using a wooden spoon or potato masher, gently break apart the jackfruit pieces so that there's a mix of small tender chunks and stringy pieces. Do this until you have a texture you're happy with, and don't worry if some black beans get mashed up in the process.
Next, stir in the lime juice and half of the chopped coriander. Continue to cook for another few minutes until the liquid has evaporated and you have a fairly thick mix. If the mix looks a little too dry, you can add more water or stock to loosen it up. Adjust the seasoning then turn off the heat and set aside.
Warm the tortillas according to package instructions. Once ready, add a heaped spoonful of the jackfruit filling to the centre and any other toppings you like (pico de gallo, guacamole etc. – see recipe notes). Sprinkle over some fresh coriander and serve.