1. Chop pumpkin into small pieces.
2. Boil 3 cups of water in a large sauce pan and add the pumpkin pieces.
3. Add rice and stir well.
4. Add till, walnuts, cinnamon and sugar and stir well.
5. Add 1/2 cup of olive oil and stir well till all ingredients are blended well.
6. Grease a baking pan well with butter.
7. Add half your pastry sheets on the bottom of the baking pan, brushing each one with olive oil.
8. Pour mixture in the baking pan making sure it covers the entire area of the baking pan.
9. Add the remaining pastry sheets on top, brushing each one with olive oil.
10. Use a sharp knife to make several diagonal incisions on the top layer of pastry sheets.
11. Brush top pastry sheet with olive oil again.
12. Sprinkle a little bit of water over it with your hands.
13. Bake in preheated oven at around 180 C (350 F) for 1 hour.
14. Cut pie in pieces while in baking pan and serve.