Begin by grating 600 g of starchy potatoes into a large bowl. Soak in cold water with a pinch of salt for 15 minutes, then drain and rinse well.

Heat 2 tablespoons of olive oil in a skillet over medium heat. Add 1 chopped green onion and sauté until softened, about 3 minutes.

Add 150 g of baby spinach to the skillet with the onions, season with salt and pepper, and cook for 2-3 minutes until wilted.

Incorporate 200 g of sliced champignon mushrooms, 1 teaspoon of dried oregano, salt, and pepper to taste. Sauté for about 8 minutes.

Drain the soaked potatoes, squeeze out excess water, and combine with 80 g of shredded mozzarella, 2 large eggs, 2 tablespoons of chopped parsley, and oregano in a bowl.

Preheat the oven to 200°C (390°F) and oil a 9-inch round baking dish.

Press the potato mixture into the baking dish to form the crust, and bake for 35-40 minutes until golden brown.

Remove the crust from the oven and layer the sautéed spinach and mushroom mixture inside. Top with 120 g of torn mozzarella fior di latte and 30 g of grated Parmesan.

Return to the oven and bake for an additional 10-15 minutes until the cheese is bubbly and golden.

Allow the pie to cool for 5 minutes before serving, garnishing with extra Parmesan and fresh parsley.