1. Preheat the oven to 350 degrees F. Butter a 9 x 13-inch baking dish.
2. In a large skillet, heat 1 tablespoon of the oil over medium-high heat and add the spinach in handfuls, adding more as the spinach starts to wilt. Cook until all of the spinach is wilted and bright green, about 3 minutes. Transfer the spinach to a colander and drain any excess liquid.
3. Wipe the skillet clean, add the remaining 1 tablespoon oil and then add the scallions. Cook until soft, about 3 minutes. Add the spinach to the skillet with the scallions and cook for an additional 1 to 2 minutes. Transfer to a large bowl and add the ricotta cheese, feta cheese, Parmesan cheese, eggs, dill, parsley, nutmeg, salt, and pepper.
4. Spread half of the filling into the baking dish. Cover with 2 pieces of the phyllo pastry. Brush lightly with melted butter. Top with 1 piece of phyllo. Spread the remaining filling over the phyllo. Top with 2 more pieces of phyllo and brush with melted butter. Top with remaining piece of phyllo and brush with melted butter. Using a sharp knife, mark 12 squares, or more if a smaller portion is desired, by cutting through the top layers of the pastry.
5. Bake for 45 to 55 minutes, until the phyllo pastry is golden, and the filling is bubbling. Use a sharp knife to cut through the squares. Arrange on a platter and serve.