Preheat your oven to 350°F (175°C). Gather your materials, including an 8x8 inch baking pan, parchment paper, and mixing bowls.

Grease the 8x8 inch baking pan to prevent sticking. Line it with parchment paper, leaving some overhang.

In a heatproof bowl, combine the dark chocolate and unsalted butter. Melt them together gently using a double boiler or microwave in 30-second intervals until smooth.

Once the chocolate and butter mixture has cooled slightly, stir in the brown sugar until well blended. Then, add the large eggs one at a time, whisking thoroughly after each addition.

Gently fold in the all-purpose flour using a spatula, being careful not to overmix.

Add the pistachio cream to the brownie batter and use a knife to create a marbled effect.

Pour the brownie batter into the prepared pan and smooth the top. Bake for 25-30 minutes, or until a toothpick comes out with moist crumbs.

Let them cool in the pan for about 10 minutes, then transfer to a cutting board to cool completely.

Cut the cooled brownies into squares and roll each piece in crushed pistachios.