• Pre-heat your oven to 370℉/180℃. Line an 8x8" baking pan.
• 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. Alternatively, set up a double boiler. Do this by placing a heatproof bowl over a small pot of simmering water. Add the chocolate to the heatproof bowl and stir until melted. 
• In a large mixing bowl, whisk together melted butter and both sugars until fully combined (3-5 minutes). Add in the eggs and whisk again. Finally, add the melted chocolate and whisk to combine.
• Add the flour, salt and cocoa powder. Fold gently with a rubber spatula or wooden spoon until just combined. 
• Pour the batter into the lined pan. Bake 22-25 minutes. Remove and let cool before the next step.

For the Ganache

• Chop the chocolate up into small pieces if using block chocolate (chocolate chips are fine too). Place the chocolate in a heatproof bowl/jug.
• Heat the cream over a medium heat in a small saucepan. Once it has started simmering, pour it over the chocolate. Leave for 2 minutes, then whisk to create a thick, glossy chocolate ganache. Pour over the baked brownies. Let cool.

For the Glaze

• Whisk together the powdered sugar and milk. It should be really thick. Put into a piping bag with a very small nozzle, or I use a sandwich bag. Seal and snip off a tiny corner to pipe through. You may want to practice piping on a piece of baking paper it to check the thickness/how it pipes.
• Pipe looping swirls onto the brownie like in the photos. Let set before slicing and serving!