Place the spring onions, chillies & coriander leaves in a food processor and pulse until you get a uniformly coarse mixture. Or, if doing it by hand, chop them all very, very finely.
Transfer to a bowl and add the grated cheese. Taste and season with salt and pepper if needed*. Add any other ingredient, if using, and mix well. Cut the naans in half along the width and divide the mixture equally on the top of all pieces.
Heat a frying pan over medium heat, then add a tsp of oil. Carefully put one half of naan in the pan. Cover with a lid, then turn the heat down to low. Cook for 3-5 minutes until the cheese melts. Repeat with the other 3 pieces. You can, if you so wish, grill the naans too. I have even microwaved them just until the cheese melts, although if taking this route, make sure you don't overcook it.