Place a medium saucepan on the stove and add the butter, sugar, and cocoa powder. Turn the heat to medium and cook, stirring constantly, until the butter melts and the mixture begins to bubble gently, about 2-3 minutes. You'll hear a soft bubbling sound and see the mixture turn glossy and smooth.
Remove the saucepan from the heat and stir in the vanilla extract. Then, quickly add the oats and stir vigorously with a spoon until the oats are fully coated with the chocolate mixture. The mixture will become thick and sticky, pulling away from the sides of the pan.
Using a spoon or small cookie scoop, drop spoonfuls of the mixture onto the prepared parchment-lined baking sheet. Shape each cookie into a rustic round with the back of the spoon if desired. Leave some space between each cookie as they will spread slightly.
Let the cookies sit at room temperature for about 15-20 minutes, or until they firm up and develop a shiny, crackled surface. For faster setting, place the tray in the fridge for about 10 minutes. You’ll notice the cookies become firmer and more cohesive as they cool.
Once set, transfer the cookies to an airtight container. They stay chewy and chocolatey at room temperature for up to 3 days or can be frozen for longer storage. Enjoy these nostalgic treats whenever you crave a quick, satisfying chocolate fix.
