1. Add sugar and water to a heavy bottomed saucepan; stir a little so it sits in a flat, even layer.
2. Warm pot over medium heat and cook until sugar dissolves, turns clear, and starts to bubble. (it will be cloudy at first, but wait 3-4 minutes for it to go clear)
3. Continue to stir so it doesn't crystalize. Sugar will form clumps. Stir until clumps turn into a deep amber color like honey. (this may take 8-12 minutes)
4. Carefully add butter and whisk until completely melted. Remove from heat.
5. Slowly stir in cream, whisking continuously.
6. Whisk in vanilla and salt.
7. Set aside to cool in the pan for 10 minutes, then pour into lidded glass jar and allow to cool completely. It will thicken as it cools.