Use for dipping Apples, Marshmallows, Chocolates or Nuts. Combine milk, sugars and corn syrup in a heavy saucepan. Set over medium heat and stir with a wooden spoon until all of the sugar is dissolved. Wash down the sides of pan with a pastry brush dipped in hot water. Place a candy thermometer into the pan; stir frequently washing down the sides of the pan when needed. At 236°F (113°C), start testing for consistency by dropping a small amount in ice water. At 242°F (117°C) or correct consistency, remove from heat. Stir in butter and vanilla; allow to cool undisturbed for about 10 minutes.