In a heavy pan, combine sugar, butter, half & half and whole milk. Bring to full boil over moderate heat. Stir constantly. Boil 5 minutes stirring constantly. Remove from heat. Add peanut butter morsels, stir until morsels melt and the mixture is smooth. Add marshmallow crème & vanilla extract. Beat till well blended. Pour into a 9 x 13 baking pan. Sprinkle peanuts over top (optional). Let cool.