1. Chop the almonds and walnuts roughly and toast them with the pine nuts in a dry ovenproof frying pan or skillet until scorched and fragrant.
2. Mash the feta with a fork in a large bowl and stir in the eggs. Add the nuts and almond pieces when cooled.
3. Place the pan back on the hob over medium-high heat and add a small knob of butter. Gradually add in the spinach, twisting it around with tongs to wilt it evenly; and adding more when there’s space. Leave it to cool. Melt the rest of the butter in a small pan or in the microwave on very low power.
4. Place a large square of baking parchment on the worktop. Working quickly so it doesn’t dry, prepare the filo pastry: place two sheets over the parchment, overlapping horizontally, so they form a square the size of the longer side of the pastry. Brush the filo liberally with the melted butter, sprinkle with salt, pepper, smoked paprika and red pepper flakes. Layer the next two sheets, brush, sprinkle and repeat with the last two. Cover the pastry with a tea towel while it waits.
5. Scrape the spinach into the bowl with feta and eggs and stir it in with the feta mixture and the pinch of nutmeg. Wipe the pan with a paper towel. Preheat the oven to 190C/375F/gas 5.
6. Carefully lift the pastry layers with the parchment and press it, parchment and all, into the pan with a sizeable overhang on all sides. Sprinkle the cheddar over the bottom. Spoon the filling into the pastry evenly and fold over the overhanging pastry to cover the pie completely. Place in on the hob over quite high heat to start the bottom off, while you brush the top of the pastry with any remaining butter. After a couple of minutes transfer the pan into the oven.
7. Bake for 30-40 minutes until golden and crispy including the sides and bottom (you can peek carefully underneath by pulling up the parchment).
8. Let the pie stand at least 15 minutes before cutting slices with a serrated edge. In fact it tastes the best just a little warmer than room temperature.
Serve with green salad.