Gather all ingredients. Preheat the oven to 350 degrees F (180 degrees C).

Place pistachios in a food processor and pulse until very finely chopped. Add in chocolate bar pieces and pulse a few times until finely chopped. Set aside 1/4 cup for topping.

Whisk tahini and pistachio cream together in a bowl until combined; set aside.

Brush the bottom and sides of a 9x13-inch baking dish with melted butter. Place down 2 phyllo sheets and brush butter in a thin layer over the surface. Top with another sheet and brush with butter. Repeat the process until there are 8 sheets on the bottom layer.

Drizzle half of pistachio cream over pastry and sprinkle with half of pistachio mixture. Top with 1 phyllo sheet; brush lightly with butter. Repeat this process 3 more times until there are 4 buttered sheets.

Drizzle on remaining pistachio cream and sprinkle on remaining pistachio mixture. Top with 6 to 8 phyllo sheets, each brushed with butter.

Using a sharp knife, cut into diamond or square shapes all the way to the bottom of the pan. Drizzle over any leftover melted butter if desired.

Bake in the preheated oven until baklava is golden brown and crisp, 40 to 45 minutes.

While baklava bakes, add water and sugar to a small saucepan and bring to a boil, stirring occasionally until sugar is dissolved. Stir in honey; reduce heat slightly, and simmer until syrupy, 15 to 20 minutes. Remove from heat.

Remove baklava from oven and immediately pour sugar syrup evenly over it. Sprinkle with reserved 1/4 cup pistachio mixture. Let cool completely before serving, at least 2 hours.

Serve in cupcake papers. This freezes well. Do not cover it tightly as it could become soggy.