Preheat your oven to 375°F (190°C).
Place the cooked spinach in a clean kitchen towel and squeeze firmly to remove every drop of excess moisture until the spinach is very dry.
In a medium mixing bowl, whisk together the large egg and egg whites until smooth.
Stir in the crumbled feta cheese, minced garlic, chopped fresh dill, sea salt, and black pepper.
Add the dried spinach to the egg mixture and stir until the spinach is well-distributed.
Lightly brush a small oven-safe baking dish or ramekin with half of the olive oil.
Layer one sheet of phyllo dough into the dish, folding the edges to fit, and brush lightly with the remaining oil before adding the second sheet.
Pour the spinach and egg filling into the center of the phyllo-lined dish.
Fold the overhanging edges of the phyllo dough over the top of the filling to partially cover it.
Bake for 25 to 30 minutes, or until the egg filling is set and the phyllo pastry is golden brown and flaky.