Preheat your oven to 320°F (160°C). For fan and convection ovens, it's 285°F (140°C). Line an 8x8-inch tin with baking paper.
Melt the dark chocolate and the butter together over low heat on the stove then set aside to cool for around 10 minutes.
To a large bowl, add the sugar, eggs and vanilla extract. Using an electric whisk or stand mixer, whisk it all together for a few minutes until it becomes super pale and has increased in volume.
Fold the melted butter/chocolate mixture into the whisked egg/sugar mixture. Then add the flour and the cocoa powder. Mix gently until well combined then stir in the chocolate chips.
Transfer the brownie batter to your tin and spread it out evenly.
Bake for around 35-40 minutes until the brownies have risen and are pulling away from the tin slightly. There should be a very slight wobble in the middle.
Leave them in the tin until cool then transfer them to the fridge overnight to set (or freeze for 2 hours if you're in a hurry).
Once set, remove them from the tin and spread the chocolate frosting on top.
Stick on the 4th July sprinkles, cut the brownies into squares then top each one with a flag decoration.