• Pre-heat your oven to 170℃/370℉. Line an 8" Square Pan with greaseproof paper.
• In a small bowl, break up the dark chocolate and melt in the microwave in 20 second intervals, stirring in between to make sure it doesn't burn.
• In a large mixing bowl, whisk together melted butter and both sugars. With an electric/stand mixer, go for a solid 3-5minutes so it is totally combined. Add in the eggs and coffee/coffee extract and combine again.
• Now, add the melted dark chocolate slowly (check it first, to make sure it isn't so hot that it will cook the eggs) and combine once again. 
• Add the flour and cocoa powder, plus a pinch of salt. Fold gently into the wet mixture with a rubber spatula or wooden spoon until just combined. Fold in the chopped chocolate. 
• Pour the batter into the lined pan and bake for 30 minutes. Let cool on a wire rack before making the frosting.

For the Frosting

• Add the butter and the coffee liqueur (or just coffee if making alcohol free) to a large mixing bowl. Beat with a whisk on high for a minute to soften/combine everything.
• Add half the icing sugar, whisk on high. Then add the remaining half and whisk everything on high until fluffy. Add coffee liqueur/icing sugar as required to meet your desired consistency. Spread over the cooled brownies, top with a little extra cocoa powder/hot chocolate powder, slice and serve!