Add potatoes to a pan of boiling water and boil until soft.
Meanwhile, heat olive oil in a frying pan and add onions.
Sauté on a medium heat until they start to go translucent.
Now add spinach leaves and stir until they wilt.
Add a generous splash of cold water and stir in the tomato puree.
Add chilli flakes and salt and pepper then mix.
Simmer for 5 minutes or so.
Once potatoes are soft, drain, fork through and add to the spinach mixture.
Stir it all together and allow to cool.
Preheat oven according to instructions on puff pastry.
Lightly grease a baking tray.
Take one puff pastry square at a time and place two teaspoonfuls of mixture on the top edge of the pastry, leaving a gap of around 1cm along the top.
Now take the bottom edge and fold it over the filling, tucking it underneath at the other side.
Place each roll on your baking tray, fold side down, leaving a generous gap between each roll.
Lightly brush the top of each roll with beaten egg or milk.
Place in the centre of your oven and bake until the pastry has puffed and turned golden.