Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe baking dish.
Sauté the chopped green onions in a pan with a splash of water until soft, then add the spinach and cook until completely wilted.
Transfer the cooked spinach to a mesh strainer and press firmly with a spoon to remove all excess liquid.
In a medium mixing bowl, whisk together the egg whites, Greek yogurt, crumbled feta, dill, sea salt, black pepper, and nutmeg.
Gently fold the drained spinach and onions into the egg white mixture until well combined.
Lay one sheet of phyllo dough into the baking dish, brush lightly with olive oil, and layer the second sheet on top.
Pour the spinach filling into the center and fold the overhanging phyllo edges inward to create a rustic border.
Bake for 25-30 minutes until the filling is set and the phyllo crust is beautifully golden and crisp.