Melt the sugar - Place sugar and water in a heavy-bottomed saucepan and stir until combined. Set the pan over medium-low heat and stir until it melts (don’t set it over too high of heat or it can crystallize). Once the mixture turns clear and starts to simmer, stop stirring and swirl the pan occasionally until the mixture is completely liquid and very light amber in color (it takes about 6-8 minutes on my stove). It's done when it's golden, don't brown too much or the caramel will be bitter. If there are any sugar crystals at the edges, they will melt into the mixture as you swirl, especially toward the end.

Add the butter - Reduce the heat to low and carefully whisk in half of the softened butter cubes, then stir in the rest. The mixture will bubble vigorously — that’s normal. Keep whisking until the butter is fully incorporated. If it separates, remove from the heat and whisk until it comes together.

Add the cream - Slowly stream in the warm cream while whisking constantly. Again, it will bubble up and steam. Keep whisking until smooth, then remove from heat. If you want to double-check with a thermometer, caramel is done when it reaches 220˚F.

Finish with vanilla + salt - Turn off the heat and whisk in vanilla and salt. Taste and adjust salt as needed.

Cool and store - Let cool slightly before using. It will thicken up quite a bit as it cools. Store in an airtight container in the fridge for up to 2 weeks. It firms up when refrigerated. Re-warm gently to drizzle.