Preheat your oven to 375°F (190°C).
Place the thawed spinach in a clean kitchen towel and squeeze forcefully to remove as much liquid as possible until the spinach is very dry.
In a medium mixing bowl, whisk together the liquid egg whites and nonfat Greek yogurt until smooth.
Stir in the crumbled feta cheese, chopped green onions, fresh dill, sea salt, black pepper, and nutmeg.
Fold the dried spinach into the egg mixture, breaking up any clumps to ensure it is evenly distributed.
Lightly brush a small oven-safe baking dish or ramekin with a small amount of olive oil.
Lay one sheet of phyllo dough into the dish, allowing the edges to hang over, brush very lightly with oil, and top with the second sheet.
Pour the spinach and egg custard into the center of the phyllo dough.
Gently fold the overhanging edges of the phyllo back toward the center, partially covering the filling.
Bake for 30 to 35 minutes, or until the filling is set and the phyllo is golden-brown and crisp.