Bought puff pastry is a good substitute for sheets of fila pastry or bread dough rolled thin with which it is variously made.
Wash the spinach well in plenty of water and remove large stems. Drain and squeeze out the excess water. You do not need to chop the leaves.
Fry the onion and spring onions gently in the oil until soft and transparent but not coloured. Put the spinach in the pan with the dill or fennel leaves and let it cook in its own juice with no extra water. It will need turning with a wooden spoon