Grab a 9-inch round cake pan. Lightly grease it, or line it with parchment paper so the cookie cake lifts out easily later.

In a medium-sized pot, add sugar, butter, milk, and cocoa powder. Set it over medium heat. Stir every so often until it starts to boil really boil, with big bubbles rolling across the surface.

Once it’s reached a full rolling boil, let it go for exactly one minute. Then take it off the heat right away. Boiling it too long can make the final texture crumbly.

While it’s still hot, stir in the vanilla, a pinch of salt, and chunky peanut butter. Mix until everything is nice and smooth.

Dump in the quick oats and stir until they’re fully coated. If you want chocolate chips in there, fold them in now. Some might melt and swirl into the mix that’s normal and delicious.

Scoop the mixture into your prepared pan. Use a spatula to press it down into an even layer. Pop the pan in the fridge for at least an hour. You want it to set up firm so it’s easy to slice.

Once it’s firm, slice it however you like bars, squares, or wedges. You can eat them chilled straight from the fridge or let them come to room temp before serving.