01 - In a large mixing bowl, combine the all-purpose flour and salt. Add the cold, cubed unsalted butter and use your fingertips to rub it into the flour mixture until it resembles coarse crumbs.
02 - Gradually incorporate the cold water, mixing until the dough just comes together. Form the dough into a disc, wrap it tightly in plastic wrap, and refrigerate for a minimum of 30 minutes.
03 - Heat the olive oil in a large skillet over medium heat. Sauté the finely chopped onion for 3 to 4 minutes until softened. Add the minced garlic and cook for an additional 1 minute until fragrant.
04 - Add the fresh spinach to the skillet and cook until it is wilted and any excess moisture has evaporated, approximately 5 minutes. Allow the cooked spinach to cool slightly.
05 - Stir in the chopped fresh parsley, chopped fresh dill, ground nutmeg, black pepper, and salt. Remove the skillet from the heat and let the mixture cool completely.
06 - In a separate large bowl, combine the cooled spinach mixture with the crumbled feta cheese, lightly beaten eggs, and lemon zest. Mix thoroughly until all ingredients are well combined.
07 - Preheat your oven to 375°F. On a lightly floured surface, roll out two-thirds of the chilled pie dough to fit the base and sides of a 9-inch round pie tin or a shamrock-shaped tin. Gently press the dough into the tin and trim any excess.
08 - Evenly spoon the spinach-feta filling into the prepared pie crust.
09 - Roll out the remaining pie dough. Using a cookie cutter or knife, cut out shamrock leaf shapes. Arrange these dough shapes on top of the filling, overlapping them slightly to create a festive design.
10 - Brush the pastry topping with the beaten egg wash. If desired, sprinkle with sesame seeds or poppy seeds for garnish.
11 - Bake the pie for 35 to 40 minutes, or until the crust is golden brown and the filling is set.
12 - Allow the pie to cool for at least 10 minutes before slicing and serving.