Fry the chopped onion in a pan with a drizzle of olive oil.
Add the spinach and cook on medium heat for a few minutes until wilted.
Chop the spinach and transfer to a bowl.
Add the ricotta, 1 egg, the grated Grana Padano Riserva, salt, pepper, nutmeg and mix well.
Line a round tin with 1 roll of puff pastry, prick the surface with a fork and then fill with the spinach mixture.
Using a spoon, carve 4 small holes in the spinach, break 1 egg into each hole and then cover with a roll of puff pastry. Bake in a preheated oven at 180 °C for 30-35 minutes.
Serve the Torta Pasqualina warm or cold.