In a mixing bowl, combine the finely chopped walnuts or pistachios with granulated sugar and ground cinnamon. Stir well until evenly distributed.

Preheat your oven to 350°F (175°C) and brush a baking dish with melted butter.

Lay half of the phyllo dough sheets in the prepared baking dish, brushing each with melted butter.

Sprinkle an even layer of the nut filling over the phyllo sheets.

Layer the remaining phyllo sheets on top of the nut mixture, brushing each with butter.

Using a sharp knife, carefully cut through all layers to shape the baklava into a circular wreath.

Bake for 25-30 minutes, or until the top is golden brown.

Combine honey, water, and sugar in a saucepan over medium heat and simmer for 5-7 minutes.

Warm milk and sugar together, then combine egg yolks, cornstarch, and vanilla in a separate bowl. Gradually add the warm milk to the yolk mixture.

Cook the combined mixture until it thickens and bubbles gently.

Pour the cooled honey syrup evenly over the hot baklava and let soak for 20 minutes.

Pour warm custard into the center of the wreath, dust with powdered sugar, and serve.