Thaw phyllo dough and keep covered with plastic wrap or wax paper and a damp cloth to prevent drying.

Grind walnuts coarsely.

Mix ground walnuts with sugar and orange blossom water until well blended to make the filling.

Butter a 12 x 16 inch baking pan.

Render the butter.

Layer one package of phyllo sheets in the pan, buttering generously between each sheet.

Mix 2-3 tablespoons of water with the walnut mixture and spread evenly over the last phyllo sheet.

Repeat layering with the second package of phyllo, buttering each sheet.

Butter the top layer.

Cut into diamond shapes, dipping the knife into hot water for easier cutting.

Pour any remaining rendered butter over the cut baklawa.

Bake at 350 degrees F (175 degrees C) for 45 minutes to 1 hour, or until the bottom is done and the top is golden brown.

If the top isn't browning, broil briefly, watching carefully to avoid burning.

Mix sugar and water in a saucepan and bring to a boil.

Boil for 15-20 minutes.

Remove from heat and add lemon juice and orange blossom water to the syrup.

Stir and let the syrup cool completely.

Pour the cooled syrup over the baked baklawa.

Let baklawa cool before serving.