If desired, substitute about 15 ounces frozen spinach, thawed, for the fresh. The important thing is to press as much liquid out of the spinach as possible to ensure a crisp crust.

Stem, wash well, and coarsely chop:

Heat in a large skillet over medium heat:

Add and cook until softened, 5 to 7 minutes:

Add the spinach a handful at a time. Cook until the spinach is wilted and the liquid is released, about 5 minutes. Increase the heat to high and cook, stirring often, until the liquid is evaporated and the spinach is dry, 7 to 10 minutes. Stir in:

Let stand until cool enough to handle, then transfer to a colander and squeeze to remove the excess liquid. Beat in a medium bowl:

Add the spinach mixture along with:

Lightly oil a 13 × 9 × 2-inch baking dish. Melt:

Unroll on a dry work surface:

Trim the dough into a 9 × 13-inch rectangle. Cover with a dry towel and cover the dry towel with a damp towel. Lay 1 sheet of phyllo in and up the sides of the prepared baking dish and brush lightly with butter. Top with 7 more phyllo sheets, brushing each lightly with butter. Spread the spinach mixture over the phyllo. Top with 8 more sheets, brushing each with butter. Roll the overhanging phyllo from the sides to form a border all the way around. With a thin, sharp knife, cut the pie into squares or diamonds, but do not cut through the bottom or the filling will leak onto the pan. Refrigerate for 30 minutes.

Preheat the oven to 375°F.

Bake the pie until crisp and golden, about 45 minutes. Remove from the oven and let cool for a few minutes. Cut the squares or diamonds right through to the bottom and serve.