Preheat your oven to 160℃/320℉ (or 140℃/290℉ for fan and convection ovens) then line an 8x8-inch tin with baking paper. Set aside for now.
Melt the dark chocolate and the butter together over low heat on the stove then set it aside to cool for around 10 minutes.
To a large bowl, add the sugar, eggs and orange extract. Use an electric whisk to whisk it all together until pale and silky.
Fold the melted chocolate mixture into the egg/sugar mixture. Then add the flour and the cocoa powder. Mix gently until well combined.
Crush 1 pack of Oreos into chunks then mix them into the brownie batter along with the chocolate chips. Transfer it to your lined tin then top with remaining Oreos.
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 (or at least 6 hours) until solid. This is key to the fudgy texture!
Once set, cut them into squares and enjoy.