Spread the sugar in an even layer in a large heavy-bottomed saucepan or skillet. Pour ½ cup of the water over it. Don't stir.
Without stirring heat the sugar and water to a boil over medium heat.
Watch the sugar carefully, it will go from clear, to a champagne color, to a light golden color to amber in a few minutes. Do not stir.
When the sugar is a deep amber color and just starting to smoke, remove it from the heat. Carefully add the other ½ cup of water, being careful because it might spatter and steam. Whisk it smooth, wearing oven mitts to protect yourself from hot splatter.
Stir in whiskey and let it come to room temperature.
Store in the fridge for up to a month. Reheat by placing in a container of hot water or gently in the microwave.
Notes
You can use more or less whiskey depending on taste. This non dairy version uses no cream or butter, so it is perfect for those restricting their dairy intake.