In a saucepan, combine the sugar, cocoa, milk, and butter. Place over medium heat. Bring ingredients to a boil, stirring constantly. Boil for 1 1/2 minutes. (This is the only tricky part of the recipe. Boil too long, and they are very hard to spoon out of pan. Not enough boiling and they are too soft to mound into cookies). I begin timing the boiling as soon as I see small bubbles. Don't wait until there is a rolling boil to time.
Remove from heat. Stir in vanilla, salt, peanut butter, and oats.
Drop by rounded spoonfuls onto waxed or parchment paper. I use a tablespoon. Size of spoon determines how many servings you will have.
Allow cookies to cool and set up - approximately one hour. Store in an airtight container.