01 - Line a baking sheet with parchment paper and set aside.
02 - In a medium saucepan over medium heat, combine the granulated sugar, unsalted butter, whole milk, unsweetened cocoa powder, and salt. Stir constantly until the mixture comes to a full rolling boil.
03 - Continue boiling for exactly 1 minute, stirring steadily. Remove the saucepan from heat immediately to prevent overcooking.
04 - Add the creamy peanut butter and vanilla extract to the hot mixture. Stir until smooth and fully melted.
05 - Gently fold in the old-fashioned rolled oats until every oat is well coated with the chocolate mixture.
06 - Drop spoonfuls of the mixture onto the prepared baking sheet, shaping into rounds as desired.
07 - Let the cookies cool at room temperature for about 20 minutes, or refrigerate briefly, until fully set and firm.