In a medium saucepan over medium heat, combine the unsalted butter, granulated sugar, whole milk, and unsweetened cocoa powder. Stir frequently until the mixture reaches a gentle boil.

Allow it to boil for 1 minute while stirring constantly to prevent burning.

Remove the saucepan from heat and immediately stir in the vanilla extract, crunchy peanut butter, and salt until fully combined and smooth.

Add the rolled oats and mix thoroughly until evenly coated.

Using a spoon, drop spoonfuls of the mixture onto a parchment-lined tray or plate, shaping each portion into a rough cookie.

Let the cookies sit at room temperature for about 30–45 minutes, or until fully set.