01 - Preheat oven to 350°F. Lightly grease a 13x9 inch rectangular baking dish with olive oil.
02 - Warm 2 tbsp olive oil in a large skillet over medium heat. Sauté diced yellow onion until soft and translucent, about 5 minutes. Add sliced spring onions and cook 2 more minutes.
03 - Add fresh spinach in batches, cooking until wilted and any liquid has evaporated. Remove from heat and stir in chopped dill, parsley, and mint. Let cool slightly.
04 - Combine crumbled feta, ricotta, beaten eggs, salt, pepper, and nutmeg in a large bowl. Add cooled spinach mixture and mix thoroughly until well incorporated.
05 - Cover phyllo dough with a damp towel to prevent drying while working.
06 - Place one sheet of phyllo in the prepared baking dish. Brush generously with olive oil and melted butter mixture. Repeat with 6-8 sheets, brushing each layer.
07 - Spread spinach and cheese filling evenly over the layered phyllo base.
08 - Arrange remaining phyllo sheets over the filling, brushing each with oil and butter. Tuck in overhanging edges and brush the top layer generously.
09 - Use a sharp knife to score the top layers into serving-sized squares or diamonds, cutting through but not separating pieces.
10 - Bake for 45-50 minutes until the phyllo is deeply golden brown and crisp throughout.
11 - Let spanakopita cool for 10 minutes before slicing along scored lines. Serve warm or at room temperature.