Preheat your oven to 350°F (175°C) and generously brush a 9x13-inch baking dish with melted butter. Keep your thawed phyllo dough covered with a damp towel to prevent it from drying out while you work.

In a medium bowl, toss the finely chopped walnuts with the ground cinnamon and ground nutmeg until well combined.

Place one sheet of phyllo dough in the prepared baking dish and brush lightly with melted butter. Repeat this process until you have 8 buttered layers forming the bottom crust.

Sprinkle half of the spiced walnut mixture evenly over the phyllo base. Scatter half of the dark chocolate chips on top, and drop small dollops of half the ricotta cheese evenly across the surface.

Layer 4 more sheets of phyllo dough over the filling, brushing each individual sheet with melted butter. Add the remaining spiced nuts, chocolate chips, and ricotta cheese to form the second filling layer.

Top with the remaining 8 sheets of phyllo dough, making sure to brush each sheet, including the very top, with melted butter. Using a sharp knife, carefully score the top layers into diamond or square shapes, cutting almost to the bottom.

Bake in the preheated oven for 45 to 50 minutes, or until the phyllo is deep golden brown and crisp. Check halfway through and tent loosely with foil if the top is browning too quickly.

While the baklava bakes, combine the granulated sugar, water, honey, and orange zest in a small saucepan. Bring the mixture to a boil over medium-high heat, then reduce the heat and simmer for 10 minutes until slightly thickened. Set aside to cool.

As soon as you remove the hot baklava from the oven, slowly pour the cooled honey syrup evenly over the top, listening for the signature crackle. Let the baklava cool completely at room temperature for at least 4 hours before serving to allow the layers to absorb the syrup.