Preheat the Oven:

Preheat your oven to 350°F (175°C).

Prepare the Nut Mixture:

In a mixing bowl, combine the walnuts, pistachios (or almonds), and cinnamon.

Assemble the Baklava:

Brush the bottom and sides of your baking dish with melted butter.

Layer one sheet of phyllo dough in the dish, brushing it with melted butter. Repeat this process with 8-10 sheets.

Spread a layer of the nut mixture (about ½ cup) evenly over the phyllo.

Continue layering 5 sheets of phyllo dough, brushing each with butter, followed by more nuts. Repeat until the nuts are used up, finishing with 8-10 layers of phyllo on top.

Brush the top layer generously with butter.

Cut the Baklava:

Using a sharp knife, cut the baklava into diamond or square shapes before baking.

Bake:

Bake in the preheated oven for 45-50 minutes, or until the top is golden and crisp.

Make the Syrup:

While the baklava bakes, combine sugar, water, honey, and lemon juice in a saucepan. Bring to a boil, then reduce heat and simmer for 10 minutes. Remove from heat and stir in vanilla extract.

Add the Syrup:

Once the baklava is baked, immediately pour the hot syrup evenly over the top. Allow it to soak in as the baklava cools.

Cool and Serve:

Let the baklava cool completely before serving. This allows the flavors to meld and the syrup to set.