Line two cookie sheets with parchment paper. Set aside. Bring butter, sugar, cocoa, milk and salt to a boil on medium heat. Boil for 2 minutes. Stir in peanut butter, oats and vanilla. Stir until completely combined.
Using a small cookie scoop (1 1/2 tablespoons), drop onto prepared pans. Let them set for one hour. Store in an airtight container. They are best kept in the fridge and keep for a few days.
Video
Notes
This recipe calls for 2 cups of sugar, which makes them on the sweeter side. If you prefer them less sweet, you can reduce the sugar to 1 cup.