Add the sugar and water to a sauce pan and heat over medium-high heat.
In a separate sauce pan, heat up the cream. It needs to get to 160°-170°C (320°-340°F)
Once the sugar mixture starts to brown, swirl the pan off of the heat. Whatever you do, do not mix with a spoon. The longer you cook the caramel, the more bitter it becomes.
Off the heat, slowly add the cream, stirring continuously with a whisk. Be careful, this is when it bubbles up and starts to bubble and spit like a cauldron. That is normal. Keep pouring in the cream and whisking simultaneously. Once everything is combined, add the butter, then mix until the butter is melted and thoroughly mixed in.
Transfer to a bowl and let cool to room temperature. Then transfer to a proper storage container and store in the fridge until needed. I personally use squeeze bottles that are microwave safe, easy to heat up and serve.