Heat the olive oil in a 12-inch / 30 cm skillet over medium heat. Add the onion and cook for 4 to 5 minutes, until soft.

Add the scallions and garlic. Cook for 1 minute, until fragrant.

Add the spinach in batches, stirring until wilted and most of the liquid has cooked off, 6 to 8 minutes. Transfer to a colander and let it cool.

Once cool enough to handle, squeeze the spinach hard with your hands or press it in a clean towel until barely any liquid drips out. This is the step that matters most, wet spinach is the main reason spanakopita turns soggy.

In a large bowl, mix the squeezed spinach with the feta, dill, parsley, eggs, pepper, and nutmeg. Taste before adding salt.

Heat the oven to 180 C / 350 F. Brush a 9 x 13-inch / 33 x 23 cm baking dish with melted butter.

Lay one sheet of phyllo in the dish, letting the edges hang over the sides, and brush it with butter. Repeat with about half the sheets, brushing each one before adding the next. Keep the rest covered with a damp towel.

Spread the spinach and feta filling evenly over the phyllo base.

Layer the remaining phyllo sheets on top, brushing each one with butter, and fold the overhanging edges over the top to seal the pie.

Score the top into 8 squares or diamonds with a sharp knife, cutting through only the top few layers.

Bake for 45 to 50 minutes, until the top is deep golden brown and crisp.

Cool in the dish for 15 minutes before slicing along the scored lines.