Preheat the oven to 180°C.

In a large frying pan, heat olive oil over medium heat. Add chopped onion and minced garlic, and sauté until the onion for approximately 5 minutes or until onions become translucent.

Add spinach to the skillet and cook until it is wilted, stirring occasionally, about 5-7 minutes. Drain any excess liquid and season with salt to taste.

In a mixing bowl, beat eggs with milk and grated parmesan cheese. Add ham to the spinach mixture and mix well.

Roll out the puff pastry on a floured surface. Cut two circles: one for the bottom of the tart and one for the top.

Line a baking dish with the first circle of puff pastry. Prick the pastry with a fork. Add the spinach and ham mixture on top of the pastry to the baking dish. Pour the egg and milk mixture over the spinach and ham mixture.

Cover the mixture with the second circle of puff pastry. Pinch the edges of the pastry together to seal.

Cut a small slit in the top of the pastry to allow steam to escape during cooking.

Bake the torta pascualina for 50-60 minutes or until the pastry is golden brown. Allow to cool for 10 minutes before serving.