Begin by clearing your counter or workspace. Gather all your ingredients and tools so you can easily access everything as you cook.
In a medium saucepan, add the unsalted butter, granulated sugar, milk, kosher salt, and unsweetened cocoa powder. Heat over medium heat until the mixture comes to a gentle boil, stirring frequently to ensure the sugar dissolves completely.
Once the mixture reaches a rolling boil, let it boil for exactly 1 minute. Remove the saucepan from heat after the minute is up.
Stir in the creamy peanut butter and vanilla extract until everything is well combined and smooth.
Add the quick-cooking oats to the mixture, stirring until all the oats are evenly coated with the chocolate-peanut butter mixture.
Using a spoon, drop tablespoon-sized portions of the mixture onto a cookie sheet lined with parchment paper. Leave some space between each cookie, as they may spread slightly.
Allow the cookies to cool at room temperature for about 30 minutes or until they have set. You can speed up the process by placing them in the refrigerator.