Preheat the oven to 180ºC / 350ºF.
Place the defrosted spinach into a clean tea towel, and bring the ends up together to enclose it. Squeeze the towel over the sink or a bowl to get out as much liquid from the spinach as possible. Discard the liquid and set the spinach aside.
Add 2 tablespoons of olive oil to a large frying pan/skillet (mine was 25cm / 10 inches) and warm over medium heat. Add the leek and garlic and pan-fry until softened. About 5-7 minutes. If at anytime the leek sticks to the pan just add a touch more oil or a little water.
Add the spinach, plus salt, and pepper. Break up the clumps of spinach with a wooden spoon and stir occasionally to heat through. Again if the pan seems a bit dry just add a touch more oil or a little water. About 10 minutes. You don't want a tonne of liquid left in the pan when you're done though. Remove the frying pan from the heat and set aside to cool slightly.
Crack the eggs into a large bowl and beat with a fork to combine. Now add in the parsley, dill, parmesan, nutmeg., cooked leek and spinach then toss to combine.
Crumble in the feta and toss through. Give the mix a taste and adjust the seasoning if you think it needs more salt and pepper. Set aside.
Unroll the filo pastry and cover it with a damp tea towel so it doesn't dry out. Put the frying pan down on the bench in front of you and brush the inside liberally with olive oil. Lay one sheet of filo into the pan going left to right, pushing down the base and sides to get out as many air bubbles as possible. The edges will be overhanging and that's fine. Brush this sheet with olive oil.
Add another sheet of filo on top but this time lay it top to bottom. This will create a cross shape and the pastry should now be covering the entire rim of the frying pan. Brush this sheet with olive oil too. Now repeat the process six more times so you have 8 sheets of filo on the base. Remember to lay one sheet going left to right, brush with olive oil and lay then next sheet top to bottom.
When the final sheet has been brushed with oil, pour in the cheese and spinach mixture, and flatten out with the back of a spoon. Take it right to the edges. Next, you want to roll up the overhanging filo so that is creates the crust edge for the top (see the video or pics above if you need more help with this).
To finish off the spanakopita - scrunch the remaining sheets of filo one by one and place around the topping to completely enclose it. Brush the top and edge with olive oil and put the frying pan into the oven.
Bake for 30 minutes or until the filo pastry is golden brown.
Remove from the oven and leave to sit for 10 minutes so the filling firms up. Cut into 4 or 6 slices and serve with tzatziki and a green salad.