Allow the phyllo to thaw overnight in the refrigerator or for a few hours on the counter, following the package directions, and count out at least 20 sheets. The pastry should unroll into flexible sheets rather than crack as you separate it.

Set the oven to 350°F before starting the filling. A fully heated oven helps the assembled pastry begin baking evenly.

Soften the diced onion in the filling’s olive oil for about 5 to 7 minutes. Look for tender pieces with less raw sharpness before adding the beef.

Break the beef into the onions and cook for about 10 minutes, then mix in allspice, cinnamon, garlic powder, salt, and pepper and set the filling aside. The meat should be browned without pooled liquid, and the spices should smell warm and fragrant.

Combine the melted butter with the pastry’s olive oil and coat the bottom of a 10" x 6" pan with the mixture. An even film of fat helps the bottom sheets bake into a crisp crust.

Trim the phyllo approximately to the pan’s dimensions, allowing uneven edges to fold along the sides. Perfect rectangles aren't necessary, and folded borders will give the pie extra crunch.

Build the bottom crust with batches of 2 to 3 sheets, brushing generously between batches until you have at least 10 sheets. Each brushed surface should have an even sheen, including the corners.

Distribute the cooked filling over the bottom crust and level it with the back of a spoon. A flat meat layer supports the upper sheets without large bumps or gaps.

Cover the filling with roughly 10 more sheets, adding them in batches of 2 to 3 and brushing between batches. The upper crust should cover the meat evenly from edge to edge.

Coat the final sheet with the butter mixture, then use a sharp knife to divide the unbaked pie into pieces, retracing each cut through the bottom crust. Cut before baking so the wash can reach the inner layers and the finished top needs less handling.

Beat the milk, egg, salt, and pepper together and distribute the mixture across the cut pastry. The wash should spread over the surface and enter the knife cuts.

Bake for 45 minutes, with an optional few minutes under the broiler while watching continuously. The finished top should look golden brown and crisp, with close attention during broiling to prevent scorching.