Heat 2 tablespoons of olive oil in a skillet over medium heat. Sauté chopped yellow onion and spring onion until soft, about 5 minutes.

Add thawed and drained frozen chopped spinach along with parsley. Cook until spinach is wilted, about 3 minutes. Let cool slightly and drain excess liquid.

In a large bowl, combine sautéed onion mixture with cream cheese, cheddar cheese, grated Parmesan, nutmeg, white pepper, and salt. Mix until smooth.

Preheat the oven to 400°F (200°C). Place a cookie sheet on the lower rack.

Roll out one sheet of puff pastry to fit your tart pan, leaving overhang. Transfer pastry into pan, fill with spinach mixture, and create wells for eggs.

Crack eggs into wells. Roll out second sheet of puff pastry to cover pie, pinch edges to seal. Brush top with beaten egg and slice vents.

Bake for about 35 minutes or until pastry is golden brown and filling is bubbling.

Once baked, cool in the pan for 5-10 minutes, then on a wire rack for another 20 minutes.