Preheat your oven to 375°F (190°C). Lightly butter a 9x13-inch baking dish and set aside.

Make the filling: In a bowl, combine the crumbled feta, ricotta, chopped parsley, chopped dill, egg, and black pepper. Stir until evenly mixed. Taste and adjust seasoning — feta varies in saltiness, so hold off on any added salt until you've tasted it.

Make the butter wash: Whisk the melted butter and milk together in a small bowl. Make the top wash separately: whisk together the egg yolk and plain yogurt in a small bowl until smooth.

Unroll your phyllo dough and cover the stack immediately with a slightly damp kitchen towel to prevent drying. Work with one sheet at a time, keeping the rest covered.

Lay two sheets of phyllo in the bottom of the buttered baking dish, letting them drape slightly up the sides. Brush generously with the butter-milk wash.

Repeat with four more sheets of phyllo, brushing every sheet with the butter-milk wash as you go — you want every layer coated.

Spread the cheese and herb filling evenly over the phyllo base, all the way to the edges.

Layer the remaining phyllo sheets over the filling, again brushing each sheet with the butter-milk wash as you go. If any sheets tear, just press them down and keep layering — it won't show.

Tuck any overhanging phyllo edges down into the sides of the dish. Brush the entire top surface with the yogurt-egg yolk wash.

Sprinkle the top evenly with nigella seeds or sesame seeds if using.

Using a sharp knife, score the top few layers of phyllo (not all the way through) into the rectangles or squares you plan to serve — this prevents the top crust from shattering unevenly when you cut it after baking.

Bake for 35–40 minutes, until the top is deeply golden brown and the edges are pulling slightly from the pan. The top should feel firm and crisp when you tap it lightly.

Remove from the oven and let rest for 10 minutes before cutting fully through along your scored lines. Serve warm.