Mix 320g of brownie mix with 55ml of water to create the batter.

Grease a microwave-safe container with cooking oil and pour the brownie batter into it. Place 6 Oreo cookies on top of the batter.

Microwave for 3 minutes and 30 seconds to 4 minutes. Depending on the thickness, microwave for an additional 4 minutes, totaling around 8 minutes.

Let the brownie cool, then flip it out of the container.

Cut the brownie into pieces, ensuring each piece contains an Oreo cookie.