Preheat the oven to 350°F and grease a 9x9-inch baking pan with nonstick spray. Line the pan with Parchment paper. In a large mixing bowl, combine the brownie mix, oil, water, and eggs. Pour the batter into the prepared pan and spread it evenly. Bake the brownies for 30 to 38 minutes, until a toothpick inserted into the center comes out clean. Let the brownies cool completely.
Place the 1 tablespoon of pistachio butter in a small Ziploc bag, set it aside
In a large skillet, melt the butter over medium heat. Add the shredded katafi and stir until it becomes golden brown. Transfer it to a large mixing bowl and stir in one cup of pistachio butter and the tahini. Spread this mixture evenly over the cooled brownies.
Place the chocolate almond bark in a microwave-safe bowl and microwave in 30-second bursts, stirring between each until fully melted. Pour the melted chocolate over the brownies and spread it to cover the entire filling. Snip off one corner of the pistachio butter bag, and squeeze the butter over the chocolate layer in a zigzag pattern. Gently lift the pan and tap it on the surface a few times to help the pistachio butter sink into the chocolate.
Put the brownies in the refrigerator for 20 to 30 minutes to let the chocolate set.
Cut into individual bars and enjoy.