Step 1: Thaw the phyllo dough according to package directions, typically overnight in the refrigerator. Before use, let it sit at room temperature for at least 1 hour, still in its packaging, to prevent cracking.
Step 2: Prepare the filling. In a large skillet or pot, heat the olive oil over medium heat. Add the chopped onion and sauté until softened and translucent, about 5-7 minutes. Add the minced garlic and cook for another minute until fragrant.
Step 3: Gradually add the fresh spinach to the skillet, in batches if necessary, stirring until it wilts completely. Cook until all the liquid has evaporated. Remove from heat and transfer the spinach mixture to a colander. Press out as much excess liquid as possible – this is crucial to prevent a soggy spanakopita. Let it cool slightly.
Step 4: In a large bowl, combine the cooled, squeezed spinach mixture with the crumbled feta cheese, chopped parsley, chopped dill, lightly beaten eggs, softened cream cheese (if using), black pepper, and nutmeg (if using). Taste and add salt only if needed, remembering the feta is quite salty. Mix well until all ingredients are evenly distributed.
Step 5: Preheat your oven to 375°F (190°C). Lightly grease a large round baking pan (approx. 12-13 inches or 30-33 cm diameter) or a springform pan.
Step 6: Prepare your workstation. Have the melted butter, phyllo dough (covered with a damp cloth to prevent drying), and spinach mixture ready. Take one sheet of phyllo dough, brush it lightly with melted butter. Place a second sheet on top, and brush it with butter as well. Continue with a third and fourth sheet, brushing each with butter. You’ll have a stack of four buttered phyllo sheets.
Step 7: Along one long edge of the buttered phyllo stack, spoon a thin, even line of the spinach-feta filling, leaving about a 1-inch border on either side. Fold the long edges of the phyllo over the filling to enclose it, then roll it up gently but firmly into a long rope. This will be your first spiral segment. Don’t worry if it’s not perfect; the layers will hide imperfections.
Step 8: Carefully place this phyllo rope in the center of your prepared baking pan, coiling it into a tight spiral. Continue the process with the remaining phyllo sheets and filling, creating more ropes. As you make each new rope, attach it to the end of the previous one in the pan, continuing the spiral outwards until the pan is filled.
Step 9: Once the golden spiral spanakopita is fully assembled in the pan, generously brush the entire top surface with any remaining melted butter. You can lightly score the top layers with a sharp knife into individual serving pieces before baking, being careful not to cut all the way through.
Step 10: Bake for 50-60 minutes, or until the phyllo is deeply golden brown and crispy. If the top is browning too quickly, you can loosely tent it with aluminum foil. Remove from the oven and let it cool for 10-15 minutes before slicing and serving. This allows the layers to set and makes for easier serving.