Combine butter and chocolate chips in a microwave safe bowl and microwave in 15 second intervals (stirring in between each interval) until butter and chocolate is completely melted together. Set aside to cool for 10 minutes
In one bowl, combine flour, cocoa powder, espresso powder, and salt together and set aside
Once chocolate mix is cooled, whisk in sugar to the mix. Then beat in eggs one at a time, and mix in vanilla extract
Gently mix in dry ingredients just until combined*
Pour brownie mix on top of graham cracker crust and bake at 350°F for 33-35 minutes, or until a wooden skewer comes out clean
Remove from oven and let it cool for 15-20 minutes