COMBINE sugar, evaporated milk, butter and salt in a medium, heavy-duty saucepan. Bring to a full rolling boil over medium heat, stirring constantly. Boil, stirring constantly, for 4 to 5 minutes. Remove from heat.
STIR in marshmallows, morsels, peanut butter and vanilla extract. Stir vigorously for 1 minute or until marshmallows are melted. Pour into foil-lined 8-inch square baking pan; cool for 1 minute. Top with peanuts, pressing in slightly. Chill for 2 hours or until firm. Lift from pan; remove foil. Cut into 48 pieces.