Combine the water, corn syrup, vanilla and salt in a medium sauce pan, bring to a boil.

Remove the pan from the heat and gradually whisk in the sugar.

The icing should be slightly warmer than body temperature and the consistency of thick cream. If you dip a spoon into the fondant it should cover with a slightly translucent finish. Use the fondant immediately or store in the refrigerator, well covered.

If the fondant cools below 100°F, rewarm gently. If the icing gets too thick add a few drop of water at a time until it's thinned to the proper consistency. If it gets too thin, add a little more sugar.