Preheat oven at 355 F = 180 C.
Cook pumpkin with oil and sugar until soft and glassy.
Add cinnamon, orange zest and lime juice, stir and cook for additional 2 minutes. If you're using walnuts or pecan, add those now.
Remove from heat.
Let cool a bit then add 2 tbsp chocolate chips. Stir to incorporate evenly (if you want the chips melted, add them right after you turned the heat off).
Cut filo pastry in half then cut the halves in half again. Brush one square with butter then layer another square on top.
Place the pastry prepared as above in an aluminium muffin mold.
Repeat for all pastry squares and muffin molds.
Place the muffin molds on a baking sheet and bake in the middle of the oven for about 10 minutes or until filo pastry turns golden.
Remove from oven, let cool a bit then sprinkle additional chocolate chips as desired.
Serve cold or warm.