Spanakopita (Spinach Pie)

Heat oven to 425°. Combine spinach, feta, 3⁄4 cup oil, dill, leeks, and eggs together in a large bowl, and season with salt and pepper. Line the bottom and sides of a 9" x 13" baking dish with one sheet of phyllo dough and brush dough with olive oil; repeat layering with 4 more sheets phyllo dough, brushing each with more olive oil. Spread spinach mixture evenly over bottom of phyllo dough and then fold the edges of dough over onto the spinach mixture. Trim the edges of the remaining phyllo sheets to fit the inside of the baking dish. Top spinach mixture with the trimmed phyllo sheets, brushing each with olive oil before adding the next. Bake until phyllo is golden brown and crisp, about 45 minutes. Let cool for 10 minutes. Cut into 4" squares before serving.