In a 3-quart saucepan set over medium heat, add the sugar and water to the saucepan and stir with a wooden spoon or silicone spoon until well combined.
When the thermometer registers 350° F and the mixture is a light amber color, the caramel sauce is ready for the next stage.
Now, add all of your butter pieces to the saucepan at once and whisk until the butter is fully incorporated.