Carefully place the sugar and corn syrup in the center of a medium saucepan, being careful not to get the sugar on the sides of the pan.
Add the water by gently running it down the sides of the pan, washing any rogue sugar back into the center. Don't stir, but gently run your finger through any dry spots, allowing the water to flow through.
Once the mixture is all wet, set over high heat and bring to a boil, without stirring.
Allow the mixture to boil until the sugar just starts to turn amber along the edge. You can now stir without fear of crystalizing.
Continue cooking until the caramel just starts to smoke; be careful not to let it go too far. Pro Tip: Add the cream when the caramel turns the right hue of amber to lock in your perfect flavor. If you aren't sure what your caramel shade is, you may need to do some experimenting. Using a whisk with a long handle, carefully and slowly whisk the cream into the saucepan. The caramel will sputter. (If you add the cream too fast, it may seize.)
Continue to cook and stir the mixture, until it eventually melts and becomes smooth. Add the butter and salt and whisk until smooth. Remove from heat.
Let cool for 15 to 20 minutes, until thick. Transfer to an airtight container and store in the refrigerator for up to 4 days. Microwave for 20 seconds to loosen to a pourable consistency.
