Peel the carrots and potatoes and slice into rounds. Parboil in plenty of salted water for a few minutes..
Drain, let cool and transfer to a bowl. Dress with a drizzle of extra virgin olive oil, grated Grana Padano Riserva and chopped marjoram. Season with salt and pepper if necessary and mix well.
Line a round baking tin with parchment paper, roll out the puff pastry and fill it with carrots slices alternating with potato slices.
Sprinkle with grated Grana Padano Riserva and bake in a preheated oven at 180 °C for 30-35 minutes.
Serve the savoury pie warm.