Mix the blanched spinach leaves, cheeses and eggs in a bowl. Season with black pepper.
Brush a rectangular baking pan with olive oil. Place 1 sheet filo pastry, brush with olive oil. Place another sheet of filo pastry, brush with olive oil. Repeat with 2 more layers of filo pastry. Pour in the spinach and cheese mixture, spread evenly with a spoon.
Top with 2 layers of filo pastry, brush each layer with olive oil. Scrunch up the remaining 2 filo pastry, place over the top, brush with olive oil.
Bake in the preheated oven for 30-35 minutes until pie is set and top is golden and crispy.
Remove from the oven, leave to cool for 10 minutes. Slice and serve with salad leaves.