Chop the chocolate and add it to the melted butter along with 1/4 cup of the cocoa, and the espresso powder. Let the mixture sit for 2mins before stirring.
Add the sugars, vanilla, eggs, and salt to a large bowl and whip for 10mins.
Add the chocolate/butter mixture to the bowl and whip again until fully mixed.
Sift the flour and the rest of the cocoa into the mixture and fold until thoroughly mixed in.
Pour the mix into a baking tray and bake at 170 degrees C for 20 mins.
Remove the tray from the oven and slam it on a counter top. The top should crack and the brownies should deflate a little. Bake for another 25 mins.
Leave the brownies to cool, then slice and serve.