To make the phyllo dough
Mix and knead all of the dough ingredients by hand or mixer to make a smooth and elastic dough. Wrap dough in plastic wrap and let rest at room temperature, for about 30 minutes.
Preheat oven at 350 ℉/ 180 ℃.
Divide dough into 4 portions, roll each portion, and form into a ball. Place on plate and cover with plastic wrap to prevent dough balls from drying out while you begin to roll them out.
Mix cornstarch and 2 tablespoons flour together in a bowl. Dust a work surface and the first dough ball with the cornstarch mixture. Flatten out the dough ball and roll out into a round circle, about 50 cm / 19.68 inches in diameter. Dust again with cornstarch mixture. Set circle to one side. Roll out the remaining 3 dough balls to about the same diameter and set aside.
To make the filling
Place the spinach in a big bowl, add 2 tablespoons salt and rub together. Let it sit for 15 minutes and then squeeze the liquids out of the spinach with your hands.
Place the squeezed spinach with rest of herbs in a big bowl. Add spring onions, leeks, garlic powder and red onion and mix well. Add the entire remaining ingredient and mix well.
To assemble the pie
With a pastry brush, lightly coat the bottom and sides of a round 15-16 inch/ 38 -40 cm pan with olive oil.
Place the 1st phyllo in a pan and brush with olive oil and continue with the 2nd phyllo. Spread the filling evenly over the last layer.
Cover the filling with the 3rd phyllo, brush with olive oil and top with the last one. Brush again with olive oil and sprinkle with a bit of water.
With a sharp knife, score the top phyllo layer into rectangles, being careful not to cut all the way through to the filling.
Bake in the lower level of the oven for about 45 minutes, until golden brown. Remove and let it cool. Cut into squares and serve warm or at room temperature.
