Preheat your oven to 375°F.
Finely chop the green onions and mince the garlic clove.
In a non-stick skillet over medium heat, sauté the onions and garlic with a splash of water until softened and fragrant.
Add the fresh spinach to the skillet in batches, cooking until completely wilted.
Transfer the cooked spinach to a clean kitchen towel or fine-mesh sieve and squeeze out every drop of excess liquid to ensure a crisp crust.
In a medium mixing bowl, whisk together the large egg, egg whites, Greek yogurt, crumbled feta cheese, chopped fresh dill, sea salt, and black pepper.
Fold the squeezed spinach and onion mixture into the egg and cheese base until well combined.
Lightly brush a small oven-safe baking dish with the olive oil.
Lay the phyllo sheet into the dish, folding or trimming the edges to fit, and pour the spinach mixture evenly over the top.
Bake for 30 to 35 minutes until the filling is set and the phyllo is beautifully golden brown and crisp.