Preheat the oven to 180ºC. Line a baking tray with baking paper.
In a small heatproof bowl, combine the butter and dark chocolate. Heat a saucepan of water over low heat and place the bowl over the saucepan ensuring the base of the bowl does not touch the water. Stir the butter and chocolate until completely melted and combined. Remove from the heat and allow to cool.
Sift the flour and cocoa powder together in a large mixing bowl. Add the brown sugar and stir until well combined, ensuring there are no lumps of sugar in the mix. Make a well in the centre and set aside.
Lightly beat the eggs and add into the well in the dry ingredients. Add the melted chocolate and stir until well combined. Mix until a sticky consistency is formed but don't over mix.
Add the chocolate chips and stir gently to combine.
Using rough tablespoonfuls, roll the mixture into a ball and place on the baking tray. Arrange the balls into an offset pattern to allow for spreading and even cooking.
Place the tray into the oven and bake for 12 minutes or until just firm to touch. Remove the tray from the oven and allow the cookies to sit for 5 minutes before transferring to a wire rack to cool completely.