Preheat oven to 350 degrees F.
Grease an 8x8 nonstick square pan with cooking spray, then line with a parchment sling. Set aside.
Place brownie mix, oil, buttermilk, eggs, instant coffee, vanilla, and salt into a large bowl.
Stir until well combined.
Fold in chocolate chips/chunks.
Pour batter into prepared pan, then top with additional chocolate chips/chunks, if desired.
Bake in preheated oven for 40-45 minutes (an inserted toothpick should come out kind of gooey).
Optional - top with maldon sea salt.
Let cool in the pan for 30 minutes, then remove, cut into squares, and enjoy!
