01 - Line two baking sheets with parchment paper.
02 - Combine butter, sugar, milk, and salt in a medium saucepan. Bring to a rolling boil over medium heat, stirring occasionally. Boil for 1 minute.
03 - Remove from heat. Stir in peanut butter and vanilla extract until smooth.
04 - Add oats and mix well to combine.
05 - Drop heaping tablespoons of the mixture onto prepared sheets. Flatten slightly with the back of the spoon.
06 - Let cookies set at room temperature for at least 15 minutes, or until firm.