Heat a generous drizzle of olive oil in a large skillet over medium heat. Add the diced onion and sliced green onions, sautéing for about 3–4 minutes until translucent and fragrant.

Introduce minced garlic to the skillet, cooking for an additional minute until aromatic. Next, add the fresh spinach, stirring until wilted.

In a mixing bowl, combine the cooled spinach mixture with fresh parsley, dill, mint, crumbled feta cheese, beaten eggs, salt, and pepper. Stir thoroughly.

Brush a baking dish generously with melted unsalted butter. Keep phyllo dough covered with a damp towel to prevent drying.

Layer phyllo sheets into the prepared dish, brushing each layer with melted butter, for 8–10 layers.

Spread the filling evenly over the layered phyllo. Add another layer of phyllo sheets on top.

Score the top layers of the phyllo with a sharp knife. Bake in a preheated oven at 375°F (190°C) for 40–50 minutes.

Let cool for a few moments before slicing into squares. Serve warm.