Preheat the oven to 350°F (325°F for nonstick pans). Coat an 8x8-inch pan with nonstick spray and line it with parchment paper, leaving an overhang for easy removal.

Make the brownie batter and cookie dough following the directions on the box. Spread the brownie batter evenly into the prepared pan.

Use a small cookie scoop to place nine even scoops of cookie dough over the brownie layer in a 3x3 grid.

Bake for 34 to 38 minutes, or until a toothpick inserted about 2 inches from the side comes out nearly clean. Remove from oven and allow the bars to cool completely in the pan.

While the bars cool, melt the butter in a large skillet over medium-high heat. Add the kadayif and toss constantly for 5 to 10 minutes, until it turns golden and becomes crisp. Transfer to a heatproof bowl to cool.

Pour the melted cup of pistachio cream over the cooled kadayif and stir until every piece is tacky and coated. Spread this pistachio-kadayif mixture evenly over the cooled brookies, pressing gently so it adheres.

To make the ganache, warm the heavy cream in a small saucepan over medium-low heat until hot but not boiling. Place the chopped semisweet and dark chocolate in a heatproof bowl and pour the hot cream over it. Let sit 3 to 5 minutes, then whisk until smooth and glossy.

Pour the ganache over the pistachio-kadayif layer and level it with an offset spatula or spoon.

Place 1 to 2 teaspoons of melted pistachio cream into a small resealable bag, snip off a corner, and pipe even lines across the ganache. Drag a knife or skewer up and down through the lines to form a marbled swirl.

Chill the pan in the refrigerator for at least 1 hour, until the ganache firms. Lift the bars from the pan using the parchment overhang and slice into 9 squares. For clean cuts, run a sharp knife under hot water, dry it, and wipe between each cut.