Preheat your oven to 160℃ (140℃ for fan ovens) then line an 8x8-inch tin with baking paper.
Melt the dark chocolate and the butter together over low heat then set aside to cool to room temperature.
In a large bowl, whisk together the sugar and eggs using an electric whisk. Keep whisking for a few minutes until the mixture becomes super pale.
Gently fold the melted chocolate mixture into the egg mixture. Then add the flour and the cocoa powder and mix gently until well combined.
Fold in the chocolate chips and crushed cookies/Oreos.
Spread the brownie batter evenly into your lined tin and bake for 35-40 minutes, until they've risen and have a shiny crust on top. Set them aside to cool while you make the fudge.
Fudge layer:
Prepare the fudge by melting the condensed milk and white chocolate together in a saucepan over low heat.
Once melted, remove it from the heat and stir in the blue food colouring. Then mix in the crushed cookies/Oreos.
Spoon the fudge mixture on top of the brownies and spread it out evenly. Top with additional cookie pieces and edible eyes.
Place the brownies into the fridge overnight to set, then cut them into squares and enjoy!
Video
Notes
Store in an airtight container in the fridge for up to 3 days. They'll last for up to 1 week if you don't add any cookie pieces on top.