Preheat oven to 160 degrees Celsius. Line a square baking pan with butter paper. Leave a little bit over the corners to remove with more ease later on.
In a pot, melt your butter over low flame. Once it's melted, add your sugar and gently stir until the mixture is completely melted and looks shiny. There should be no large chunks of sugar left.
Remove your pot from the heat and add your coffee. Once it's dissolved, add your cocoa powder and whisk continuously until it's completely incorporated.
Allow mixture to cool a little for 4-5 minutes and then add your vanilla extract and mix to combine.
One by one, add in your eggs and whisk after each addition until the batter is smooth.
Finally, add your flour and chocolate chips and STIR (don't whisk) until it all comes together. Do not over mix.
Pour the brownie batter into your prepared pan and bake for 25-30 minutes or until a toothpick inserted into the center comes out slightly dirty. Allow it to cool before you frost.