It’s now time to create some caramel. Take your melted butter and whisk the heavy cream into it. Then, put the corn syrup and water in a pan and turn the stove to medium. Give the mixture a stir, and then slowly add the sugar to the pan. You want to make sure the sugar is fully combined with the liquid, so be sure to scrape the sides of the pan if you see sugar there. Once everything is nice and incorporated, keep it on the heat, using a candy thermometer to make sure it reaches 320 F.
Once you hit that temperature, add the butter and cream in small amounts, mixing each time, until all of it is in the pan. Sprinkle in your salt, and keep it on the heat until the whole thing reaches 245 F. Then, take it off the heat and let it cool for a couple minutes.
“You really do need a candy thermometer for this recipe,” Shungu advises. “If the caramel isn’t warm enough, it’ll be too soft to set. If it gets too hot, the caramel will be too hard. If you don’t have a candy thermometer, you can also use a meat thermometer — just tilt the pan so you can get an accurate reading.”