Chop the onion.

Sauté the onion in olive oil until dark yellow.

Add the lean ground beef and brown it.

Add water, salt, and pepper.

Cook until the water is evaporated.

If using, add chopped nuts.

Divide the filo dough sheets in half to create 10x10 sheets.

Grease a 9x12x3 inch baking dish.

Layer 2-3 filo sheets at a time, sprinkling with melted butter between each layer, until the first stack is used.

Spread the meat and nut mixture evenly over the filo.

Layer the second stack of filo sheets, sprinkling with melted butter between layers.

Cut the pastry into 2x1 inch squares.

Mix together the leftover melted butter, egg, milk, and a pinch of salt.

Beat with a fork.

Pour the egg mixture gently over the pastry.

Bake uncovered in a preheated 375°F oven for about 20 minutes, or until golden yellow and the milk is absorbed.