Fill the kitchen sink with cold water and give the spinach a good wash. If you have large spinach leaves you can give them a rough chop before or after the wash. Dry the spinach, I did this in batches using my salad spinner.
Heat a large frying pan or saucepan with a lid and add the olive oil. While that is heating, roughly chop your onion and spring onion and add to the pan, stir together and then lower the heat and cover to sweat.
After about 5 minutes increase the heat and start adding the spinach, in batches if necessary, based on the size of your pan. Once you have fit all the spinach in the pan season with salt and pepper a few gratings of nutmeg.
When the spinach has all wilted down, stir in the parsley and dill, and remove from the heat.
Tip the spinach mixture into a colander and leave to drain (you may want to also press down on it to remove further liquid once it has cooled a little).
In a large bowl crumble the feta and add the eggs. Add the cooled spinach and stir to combine.
In a small pan melt the butter while you set up a space to put the pie together.
Wet a tea towel and place over your phyllo pastry, once the butter is melted bring that to your work space and brush the inside of the tin you'll assemble the pie in.
Preheat the over to 180°C.
Take your first piece of phyllo pastry (covering the rest again with the wet tea towel) and brush one side with butter before place it (butter side up) in the tin, it is fine if part of it hangs over the side. Repeat this with several more pieces of phyllo until the base is completely covered and you have overhang around the entire edge of the tine, and it is about 2-3 layers thick.
Spoon the spinach mixture into the tin and smooth over. Fold any bits of overhanging pasty into the middle, covering the filling, and the use another few pieces to cover the top of the pie. If you like an extra crunchy top, you can scrunch up a few pieces of buttered phyllo and arrange over the top of the pie as well.
Brush the beaten egg over the top of the pie and follow with any left over melted butter and place in the preheated over for about 30 minutes until the top of the pie is a lovely golden brown.
Serve along side a fresh green salad, maybe some tzatziki and pita, or as part of a Greek-style spread.