Preheat the oven to 200C, fan 180C, gas 6.
Heat a medium frying pan until medium hot, add the butter and onion and sweat for 10 minutes until softened but not coloured.
Add the defrosted spinach and stir through, mixing well and heat until all the excess water has been evaporated.
Remove from the heat and stir in the nutmeg, feta cheese and pine nuts then season to taste. Set aside to cool slightly while you form the parcels.
Cut the filo sheets in half so you have large squares.
Brush 1 square with rapeseed oil and lay into the work surface. Cover at an angle with a second sheet, then brush with more rapeseed oil, then repeat with a third sheet.
Repeat so you have 4 stacks of filo layers.
Divide the spinach mixture between the filo, then loosely fold the pastry edges over the filling.
Bake in the oven for 10 minutes until golden brown and hot through. Serve with a little green salad.