In a small saucepan over low heat, combine dark chocolate and unsalted butter. Stir continuously for approximately 5 minutes until smooth.

Whisk in sweetened condensed milk, vanilla extract, and a pinch of salt until thoroughly combined and creamy.

Gently fold in graham cracker crumbs and chopped pistachios into the chocolate mixture until evenly coated.

Lightly grease an 8-inch square pan and scoop the chocolate mixture into the prepared pan, pressing it down firmly.

Place the pan in the refrigerator and allow the mixture to chill for at least 2 hours until fully set.

Remove the pan from the refrigerator and slice the bars into 12 equal pieces for serving.