Preheat your oven to 375°F (190°C) and line a large baking sheet with parchment paper.
Place the thawed spinach in a clean kitchen towel and squeeze firmly to remove every drop of excess moisture until it is very dry.
In a medium mixing bowl, whisk the liquid egg whites and Greek yogurt until smooth, then stir in the dried spinach, crumbled feta, dill, parsley, minced garlic, sliced scallions, sea salt, and black pepper.
Lay one sheet of phyllo dough on a clean work surface, brush very lightly with a small amount of melted ghee, and place the second sheet directly on top.
Using a sharp knife or pizza cutter, slice the phyllo stack lengthwise into four equal, long strips.
Place a generous portion of the spinach and egg mixture at the bottom end of each strip, then fold the corner over the filling to form a triangle.
Continue folding the triangle upward, maintaining the shape until you reach the end of the strip, similar to folding a flag.
Arrange the triangles on the prepared baking sheet, brush the tops with the remaining ghee, and bake for 20-25 minutes until the pastry is deeply golden and crisp.