Cook the spinach in a large saucepan, with just the water left on the leaves after rinsing, over a low heat until wilted and soft. Drain well pressing out the juices.
Mix the feta into the spinach with the chilli flakes, Parmesan, pine nuts and herbs. Mix in the beaten eggs with plenty of salt, pepper and grated nutmeg.
Unwrap the filo pastry and, working quickly, brush the top sheet of pastry with a little olive oil. Lay in the bottom of a lightly greased 20 cm (8 inch) loose-bottomed cake tin with the edges overlapping the rim of the tin. Brush the next sheet of pastry and lay it in the opposite direction to cover the base of the tin. Repeat with 4–6 sheets of pastry, saving 3 sheets to make a lid.
Spoon the spinach mixture into the filo pastry shell, pushing it in with the back of the spoon and to level.
Cut the remaining pastry into 5 cm (2 inch) wide strips. One by one, brush them with oil and place them on top of the spinach in a casual folded arrangement. Fold the overhanging filo towards the middle of the pie, sprinkle with sesame seeds and bake in a preheated oven, 190°C (375°F), Gas Mark 5, for 50–60 minutes. Leave to cool. When ready to serve, remove from the tin and serve with salad.