Heat 2 tablespoons of olive oil in a large skillet over medium heat. Sauté the diced onion and green onions for 3-4 minutes, until translucent and fragrant. Add minced garlic and stir for an additional minute, then add fresh spinach. Cook until wilted, about 3-5 minutes, then set aside to cool.

Once the spinach mixture has cooled, transfer it to a large mixing bowl. Add parsley, dill, mint, and crumbled feta cheese. Crack in the eggs and season with salt and pepper. Stir until well combined.

Unroll the phyllo dough carefully, keeping it covered with a damp towel. Preheat your oven to 375°F (190°C). Prepare a 9x13-inch baking dish by brushing the bottom and sides with melted unsalted butter.

For casserole-style, layer 4 sheets of phyllo in the bottom of the dish, brushing each layer with melted butter. Spread the filling evenly, then layer an additional 4 sheets of phyllo on top, brushing each with butter. Score the top layers and bake for 40-50 minutes.

For Spanakopita rolls, brush two sheets of phyllo. Place filling along one edge and roll tightly. Place seam-side down on a baking sheet and brush tops with butter. Bake for 20-25 minutes.

For Spanakopita bites, cut phyllo into strips. Place filling at one end and fold over to form triangles. Place bites on a baking sheet, brush with butter, and bake for 15-20 minutes.

Allow Spanakopita to cool for about 10 minutes before serving warm.