Begin by peeling and grating 600 g of potatoes. Soak the grated potatoes in a bowl of cold water with a pinch of salt for about 15 minutes.

While your potatoes soak, heat 2 tablespoons of olive oil in a skillet over medium heat. Add one chopped green onion and sauté for 2-3 minutes until softened.

Next, stir in 150 g of baby spinach, cooking just until wilted, about 1 minute.

Add 200 g of sliced champignon mushrooms, season with salt, pepper, and a teaspoon of dried oregano, and sauté until golden.

In a large mixing bowl, combine the drained and squeezed potatoes with 80 g of mozzarella cheese, 2 large eggs, 2 tablespoons of chopped fresh parsley, salt, and pepper.

Preheat your oven to 200°C (390°F). Brush a baking dish with 2 tablespoons of olive oil.

Press the potato mixture into the bottom and sides of the dish, creating a crust about 1/4 inch thick. Bake for 35-40 minutes.

Once the crust is baked, remove it and let it cool slightly. Spoon the sautéed filling into the crust, sprinkle with remaining cheeses.

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

Allow the pie to cool for about 5 minutes before slicing.