Bring a large pot of salted water to a boil. Add the chopped spinach in batches and blanch for 30–45 seconds until wilted. Drain immediately in a colander, pressing out as much liquid as possible with the back of a spoon. Alternatively, sauté spinach in a large skillet with 1 tablespoon olive oil until wilted. Once cooled, transfer to a clean kitchen towel or cheesecloth and squeeze firmly to remove excess moisture. Chop further if large.

Sweat aromatics

In a large skillet, heat 2 tablespoons olive oil over medium heat. Add the finely chopped onion and cook, stirring, until translucent and soft, about 6–8 minutes. Add the minced garlic and sliced green onions and cook 1 minute more until fragrant. Remove from heat and let cool slightly.

Combine filling ingredients

In a large bowl, combine the well-drained spinach, cooled onion mixture, crumbled feta, ricotta, beaten eggs, chopped dill, chopped parsley, ground black pepper, salt, and grated nutmeg if using. Mix thoroughly with a spoon or your hands until evenly distributed. Taste and adjust seasoning — remember feta is salty so use salt sparingly.

Assemble & Bake

Prepare phyllo and oven

Preheat oven to 190°C (375°F). Lightly grease a 23 x 33 cm (9 x 13 inch) baking pan with melted butter or oil. Unroll thawed phyllo sheets and keep them covered with a slightly damp kitchen towel to prevent drying out.

Layer phyllo

Place one sheet of phyllo in the prepared pan and brush lightly with melted butter (about 1 tablespoon). Continue layering 6 sheets, brushing each with butter. Let the edges overhang the pan slightly if you prefer a folded edge.

Add filling

Spread the spinach and cheese filling in an even layer over the buttered phyllo base. Smooth the top with a spatula so the filling is uniform.

Top with remaining phyllo

Layer the remaining 6 phyllo sheets over the filling, brushing each sheet lightly with butter as before. Tuck any overhanging edges inward or fold them over to seal. Brush the top layer generously with the remaining butter.

Score and egg wash

Using a sharp knife, score the top phyllo into squares or diamonds to make slicing easier after baking. Whisk together the egg yolk and 2 tablespoons milk and brush the mixture over the top phyllo. Sprinkle sesame seeds evenly if desired.

Bake

Bake in the preheated oven for 35–45 minutes until the phyllo is deep golden brown and crisp and the filling is set. If the top is browning too quickly, tent loosely with foil for the last 10–15 minutes.

Rest and serve

Remove from oven and let cool in the pan on a rack for 10–15 minutes to set. Use the scored lines to cut into portions. Serve warm or at room temperature as part of a mezze selection.