01 - Preheat oven to 350°F. Lightly grease a 13x9 inch rectangular baking dish with olive oil or butter.
02 - In a large skillet over medium heat, warm 2 tbsp olive oil. Sauté yellow onion until soft and translucent, about 5 minutes. Add spring onions and cook 2 more minutes.
03 - Add fresh spinach in batches and cook until wilted. Continue cooking until any liquid has evaporated completely. Remove from heat and stir in dill, parsley, and mint. Let cool slightly.
04 - In a large bowl, combine crumbled feta, ricotta, beaten eggs, salt, pepper, and nutmeg. Add the cooled spinach mixture and mix thoroughly until well incorporated.
05 - Keep phyllo dough covered with a damp kitchen towel to prevent drying while working. Have olive oil and melted butter ready for brushing.
06 - Place one sheet of phyllo in the prepared baking dish and brush generously with olive oil or melted butter. Repeat with 6–8 sheets, brushing each layer.
07 - Spread the spinach and cheese filling evenly over the layered phyllo base.
08 - Layer remaining phyllo sheets on top, brushing each with oil or butter mixture. Tuck in overhanging edges and brush the top generously.
09 - Use a sharp knife to score the top layers into serving-sized squares or diamonds, cutting through only the top phyllo layers.
10 - Bake for 45–50 minutes until the phyllo is deep golden brown and crisp throughout.
11 - Let the spanakopita cool for 10 minutes before slicing along the scored lines. Serve warm or at room temperature.