Preheat your oven to 350°F (175°C). Line the baking pan with parchment paper, leaving some overhang for easy removal.
In a mixing bowl, combine graham cracker crumbs, melted butter, and granulated sugar. Mix until well combined and crumbly.
Press the crumb mixture firmly into the bottom of the prepared baking pan to form an even layer. Bake for 8-10 minutes, until set and starting to brown. Remove from the oven and let it cool slightly.
In another mixing bowl, beat the softened cream cheese and granulated sugar with an electric mixer until smooth and creamy. Add eggs, one at a time, mixing well after each addition. Stir in vanilla extract.
Gently fold in the fresh blackberries and chopped pistachios into the cheesecake batter.
Pour the cheesecake filling over the crust in the baking pan, spreading it evenly.
Bake in the preheated oven for 25-30 minutes, or until the edges are set and the center is slightly jiggly.
Remove from the oven and let it cool to room temperature, then refrigerate for at least 2 hours to set.
Before serving, top the cheesecake bars with the additional fresh blackberries and chopped pistachios for a beautiful presentation.
Once chilled, lift the cheesecake out of the pan using the overhang of parchment paper and cut into 12 bars.