Line two large baking sheets with parchment paper and set aside.

In a large saucepan over medium heat, combine butter, sugar, milk, and cocoa powder. Stir frequently until butter is melted and mixture is smooth.

Bring to a rolling boil and boil for exactly 60 seconds, stirring occasionally.

Remove from heat and immediately stir in peanut butter and vanilla until fully combined.

Add oats and mix until evenly coated.

Drop spoonfuls of the mixture onto prepared baking sheets.

Let cookies cool and set for 20–30 minutes before serving.