Gather your equipment: a medium saucepan, a spoon, and a parchment paper-lined baking sheet. Set everything within reach before starting.
Combine sugar, cocoa powder, butter, and milk in the saucepan. Turn the heat to medium and stir constantly as the mixture begins to melt and bubble gently, filling your kitchen with a rich chocolate aroma.
Once it reaches a gentle boil, set a timer for 1 minute and continue stirring. You'll notice the mixture thickening slightly and becoming glossy, like a smooth chocolate sauce.
Remove the saucepan from heat and quickly stir in the vanilla extract to brighten the flavors. Then add the oats, chocolate chips, and peanut butter, stirring vigorously until everything is evenly coated and the mixture is thick and sticky.
Using a spoon, scoop dollops of the mixture onto your prepared parchment paper. Flatten each slightly with the back of the spoon for a uniform shape.
Let the cookies sit at room temperature for about 30 minutes until they firm up and develop a chewy, fudgy texture. For a quicker set, place the tray in the refrigerator for 15 minutes.
Once set, gently peel the cookies from the parchment paper. They should be shiny on top with a slight crackle and hold together when pressed.
Enjoy these chewy, chocolatey treats immediately or store in an airtight container at room temperature for up to 3 days. For longer storage, freeze them and thaw slightly before serving.
