Preheat oven to 180 degrees Celsius (350 F). Line a brownie tin with baking paper and set aside.

In a microwave safe bowl, melt the butter for 1 minute or until completely melted.

Add the baking cocoa and coffee to the butter and whisk together until smooth and combined.

Add the sugars, eggs and vanilla essence to the bowl and stir to combine.

Add baking powder, salt and flour and stir until just combine. Be careful not to overmix.

Pour the brownie mixture into the brownie tin, ensuring that it is spread evenly and smooth. Layer 12 Oreos evenly over the brownie batter in a single layer.

Place in the oven and bake for 18-20 minutes, or until just set and a toothpick inserted into the centre comes out clean. Remove from oven and set aside to cool.

Meanwhile, crush 1.5 packs of the remaining Oreos in a food processor, or with your hands if you don’t have one. Pulse/crush until it becomes a coarse crumb.

In a large microwave safe bowl, add the marshmallows and butter. Heat in the microwave for 90 seconds, and remove from the microwave. Stir to combine with a plastic spatula (otherwise the marshmallow will stick).

Pour the Oreo crumbs into the bowl with the marshmallow mix and stir to combine.

Once your brownies are out of the oven and have cooled slightly, pour the marshmallow mix over the brownies, using a plastic spatula to smooth the marshmallow mix evenly over the top of the brownies.

Crumble the remaining Oreos over the top, pressing them gentle into the marshmallow mixture to make them stick.

Allow the brownies to cool completely before cutting, or place in the fridge overnight before serving.