In a large bowl, combine the finely chopped walnuts, almonds, and pistachios. Add the ground cinnamon, ground cloves, and ground cardamom. Mix well.
Preheat your oven to 350°F (175°C).
Brush a 9x13 inch baking dish with some of the melted butter.
Unroll the phyllo dough and cut it to fit the size of your baking dish. Keep the phyllo dough covered with a damp cloth to prevent it from drying out.
Place one sheet of phyllo dough in the baking dish and brush it with melted butter. Repeat this process, layering and buttering each sheet, until you have used about half of the phyllo dough.
Spread the nut mixture evenly over the phyllo layers.
Continue layering the remaining phyllo dough sheets on top of the nut mixture, brushing each sheet with melted butter.
Using a sharp knife, cut the baklava into diamond or square shapes.
Bake in the preheated oven for 45-50 minutes, or until the baklava is golden brown and crispy.
While the baklava is baking, combine the granulated sugar, water, honey, and lemon juice in a medium saucepan. Bring to a boil over medium heat, stirring until the sugar is dissolved.
Reduce the heat and simmer for about 10 minutes, until the syrup thickens slightly. Remove from heat and stir in the vanilla extract.
Remove the baklava from the oven and immediately pour the hot syrup evenly over the hot baklava. Allow the baklava to cool completely and absorb the syrup.
Once the baklava is completely cool and the syrup is absorbed, carefully lift the pieces from the baking dish and arrange them on a serving platter.
Enjoy your meal!