Preheat your oven to 375°F (190°C) and line a small baking sheet with parchment paper.
In a skillet over medium heat, add the olive oil and sauté the diced onion and minced garlic until translucent and fragrant.
Add the chopped fresh spinach to the skillet and cook until fully wilted; remove from heat and let cool slightly.
Place the wilted spinach in a clean kitchen towel and squeeze out all excess moisture to ensure the pastry stays crisp.
In a mixing bowl, combine the squeezed spinach, cooked shredded chicken breast, crumbled feta, egg, sea salt, black pepper, dill, and parsley.
Lay one sheet of phyllo dough on the parchment, lightly mist with water or oil, and top with the second sheet.
Place the chicken and spinach mixture in the center of the phyllo, then fold the edges over the filling to create a rectangular parcel.
Bake for 20-25 minutes until the phyllo is deeply golden brown and the filling is set.
Allow the pie to rest for 5 minutes before slicing and serving.