Preheat the oven to 180°C.
Peel the pumpkin, remove the seeds then coarsely grate the flesh.
Peel the roasted chestnuts, and in a blender process them until you get crumbles.
In a large bowl, mix the eggs and sugar until light, then add the orange zest, juice, oil and chestnut crumbs. Combine.
Stir in the grated pumpkin and sieve the baking powder and flour on top. Carefully mix with a flat wooden spoon.
Line the muffin tin with paper or put silicone muffin forms onto a baking sheet. Fill them with the batter.
Bake for 30-35 minutes until golden brown.
Rest on a wire rack before serving.