Roll out the cookie base:
Place a sheet of parchment paper on your counter, then press or roll the cookie dough into a rectangle about 9×13 inches in size and roughly ¼ inch thick. This will be the foundation for your swirls.

Whip up the brownie layer:
In a mixing bowl, combine the brownie mix with oil, eggs, and water. Stir until the batter is thick and glossy — it should be easily spreadable but not runny.

Create the swirl:
Spread about ¾ cup of the brownie batter evenly over the rolled-out cookie dough. Use an offset spatula or the back of a spoon to smooth it out, leaving a small border (around ½ inch) along the edges.

Roll it up:
Starting from one long side, gently roll the dough into a tight log, similar to how you’d roll cinnamon rolls. Don’t worry if some batter peeks out — that’s part of the charm!

Chill time:
Wrap the log snugly in plastic wrap. Place it in the freezer for 1 hour or chill it in the fridge for at least 2 hours, until it’s firm enough to slice without smushing.

Bake the swirls:
Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.
Using a sharp knife, slice the dough into ¾-inch-thick rounds and space them about 2 inches apart on your trays.

Into the oven:
Bake for 10–12 minutes, or until the edges look golden brown and the centers are just set but still soft. They’ll firm up a bit as they cool.

Cool and enjoy:
Let the cookies rest on the baking sheet for 5 minutes before transferring them to a wire rack. Enjoy warm for maximum gooeyness or at room temp for that perfect chewy bite.