Line 2 baking sheets with parchment paper or silicone mats and set them aside.

In a medium saucepan over medium heat, combine the butter, sugar, milk, and cocoa powder. Stir occasionally until the butter melts and the sugar dissolves completely.

Bring the mixture to a full rolling boil and cook for about a minute, stirring frequently to prevent scorching.

Remove the pan from the heat, and immediately stir in the peanut butter, vanilla, and salt until the mixture is smooth and glossy.

Add the oats and gently fold until every oat is evenly coated, and the mixture thickens.

Using a cookie scoop or heaping tablespoon, drop mounds of the mixture onto the prepared baking sheets. Allow them to stand at room temperature until firm, about 20–30 minutes.