Yield: 24 squares
1/4 cup good olive oil
1 cup chopped yellow onion
3 scallions, white and green parts, chopped
2 (10-ounce) packages frozen chopped spinach, defrosted
4 extra-large eggs, lightly beaten
3 tablespoons freshly grated Parmesan cheese
Plain dry bread crumbs
1 teaspoon grated nutmeg
1 teaspoon kosher salt
1 teaspoon freshly ground black pepper
2 cups small-diced feta cheese (12 ounces)
3 tablespoons toasted pine nuts
24 sheets frozen phyllo dough, defrosted
1/4 pound (1 stick) unsalted butter, melted
Flaked sea salt, such as Maldon, for sprinkling
Preheat the oven to 375 degrees F.
Heat the olive oil in a medium saute pan, add the onion, and cook for 5 minutes over medium-low heat. Add the scallions, and cook for another 2 minutes until the scallions are wilted but still green. Meanwhile, gently squeeze most of the water out of the spinach and place it in a large bowl.
When the onion and scallions are done, add them to the spinach. Mix in the eggs, Parmesan cheese, 3 tablespoons bread crumbs, the nutmeg, salt, and pepper. Gently fold in the feta and pine nuts.
Brush the melted butter in a 13x9 baking pan. Place 1 sheet of phyllo dough in it and brush the dough lightly with butter and sprinkle it with a teaspoon of bread crumbs. Working quickly, slide another sheet of phyllo dough on top of the first, brush it with butter, and sprinkle lightly with bread crumbs. (Use just enough bread crumbs so the layers of phyllo don't stick together.) Pile 6 layers total on top of each other this way, brushing each with butter and sprinkling with bread crumbs. Spread the spinach filling on top of the 6 phyllo layers and continue buttering and sprinkling bread crumbs between 6 more layers of phyllo laying them on top of the filling. Butter the top layer and sprinkle with flaked sea salt and bake for 30 to 35 minutes, until the phyllo is browned and crisp. Serve hot or warm.