Spray a 9x13x2 baking pan with non-stick cooking spray.

Bring sugar, milk and butter to a rolling boil over medium heat; stir constantly. Once mixture starts to boil, allow to cook for approximately 3 minutes, before checking the consistency of the syrup. With ice water in a small bowl, allow the syrup to drop off the spoon into the ice water (one to two drops). Check consistency of mixture. If it is rubbery (like a chocolate chew), syrup is done. If it's not, allow it to cook for no more than two more minutes.

Once syrup reaches the correct consistency (234 degrees F), remove from heat. Add vanilla, marshmallow cream and peanut butter and stir until well combined. Pour into prepared pan. Allow to cool to room temperature and cut into squares (about 24 per pan or 3 lbs of fudge).