Fill a large saucepan with water and bring to a boil over high heat. Once boiling, drop a large handful or two of spinach into the water and let cook for 2 minutes. Transfer spinach into a colander and rinse under cold water. Repeat until all spinach has been wilted.
Using paper towels, squeeze spinach to remove as much water as possible. Transfer spinach to a cutting board and chop coarsely; set aside.
Add olive oil to pan and place over medium heat. Once hot, add onions. Sauté, stirring occasionally for 5 minutes. Add garlic, stir, and continue sautéing for 1-2 more minutes.
Transfer onions and garlic into a large bowl. Add spinach, ricotta, Parmesan, salt, pepper, nutmeg and 1 egg; stir until well combined.
Preheat oven to 350°F.
Spray an 8” springform pan with nonstick baking spray. (Note: The pan should be at least 3” deep.)
Roll one sheet of puff pastry into a 14” circle. Press puff pastry into bottom and sides of the prepared pan.
Pour spinach mixture into pan. Using a spoon, carefully make 5 holes in the spinach mixture. Crack one egg into each of the holes.
Roll second sheet of puff pastry into a 9” circle. Lay puff pastry over the spinach mixture and pinch edges of puff pastry together to crimp and seal the pie.
Using the back of a knife, score the top of the dough lightly over each of the 5 eggs. (Note: The score marks will both serve as steam vents as well as a guide for where to slice the pie so that you cut the eggs in half.)
Using a small bowl, lightly beat the remaining egg and brush mixture on top of the pie. (Note: The entire egg will not be used.)
Bake at 350°F for 55-60 minutes, or until top is golden brown in color.
Let cool for 30-45 minutes before releasing springform pan and slicing. Serve warm or at room temperature.