In a medium-sized saucepan, combine the water and sugar. Set over medium heat and stir occasionally until the sugar fully dissolves. Bring the mixture to a boil and let it simmer gently for 15 to 20 minutes until it thickens slightly. Squeeze in a few drops of fresh lemon juice to prevent crystallization and simmer for an additional few minutes. Remove the syrup from the heat and set it aside to cool completely while you prepare the baklava layers.

Preheat your oven to 175°C (350°F). Prepare a baking tray approximately 35 cm x 24 cm (14" x 9.5") in size. Working with one pack of filo pastry at a time, trim the sheets to fit the tray dimensions. Cover the sheets with a damp kitchen towel to keep them pliable and prevent drying.

In a small bowl, blend the melted clarified butter with the vegetable oil. Lay a single sheet of filo pastry into the tray and drizzle a spoonful of the butter-oil mixture over the top. There’s no need to brush each sheet thoroughly; a light drizzle is sufficient. Repeat this process, layering and drizzling, until all sheets from the first pack are used, forming around 28 to 30 delicate layers.

Once the base layers are in place, evenly scatter the pistachio nuts across the filo, pressing gently to set them in place without compressing the layers too much. Proceed by trimming the second pack of filo pastry and layering it over the pistachios, continuing the drizzle technique with the butter mixture between each sheet.

After placing the final filo sheet, pour any remaining butter mixture across the surface to ensure an even, golden finish. Using a sharp knife, carefully cut the pastry into diamond or square shapes, slicing all the way through to the base. The size of the pieces can be adjusted to your preference, though a 4 cm (1.5") cut typically yields about 70 servings.

Place the tray in the preheated oven and bake for 15 minutes. Then, reduce the oven temperature to 160°C (320°F) and continue baking for another 45 minutes, or until the baklava is deeply golden and crisp, with the bottom layers fully cooked through.

Once baked, remove the tray from the oven and allow it to cool slightly for about 5 minutes. Gradually ladle the cooled syrup over the baklava, ensuring even distribution. Let the baklava rest overnight, allowing it to absorb the syrup thoroughly and achieve its signature luscious texture before serving.