6tablespoons(85g)butter, cut into tablespoon-size pieces
¼teaspooncoarse, kosher salt
1tablespoonvanilla extract (see note)
Butter the bottoms and sides (get into the corners, too!) of a 9X9-inch square baking pan. (Alternately, you can line with parchment and butter the parchment - this may make it easier to pull the slab of caramels out of the pan after they have cooled in order to cut and wrap them.) Set aside.
Heat the cream in a saucepan or in the microwave until steaming. Keep warm.
For the caramels, in a large, heavy-bottomed pot (at least 5- or 6-quarts), stir together the sugar, corn syrup, and water, taking care to not splash the mixture up the sides of the pot. Clip a candy thermometer onto the side of the pan.
Bring the mixture to a boil over medium-high heat WITHOUT STIRRING or moving the pan. As it begins to boil, fill a cup with water and use a pastry brush to wash down the sides of the pan so there are no granules of sugar sticking to the sides of the pan (you probably won't need to repeat this after the sides have been well-cleaned). This prevents the caramel mixture from crystallizing in later steps.
Cook until the boiling sugar mixture registers 325 degrees F on the thermometer, about 15-20 minutes (for darker but still chewy caramels, continue cooking the sugar mixture - I've gone as high as 345 for super intense, dark caramels; beware the next step will cause much more steaming and bubbling the higher you cook this initial sugar mixture).
Slowly and carefully pour the warm cream into the caramel. It will bubble and produce a lot of steam! Add the butter and salt. The mixture will bubble high during this step but will go down after a few minutes.
Begin stirring the caramel with heatproof rubber spatula with a flat top (a flat edge does better at preventing the caramel from burning than a rounded edge). Avoiding scraping the edges of the pan, and continue to cook, stirring constantly and slowly, until the mixture reaches 245 degrees F, about 10-15 minutes (you can go as high as 248 degrees F for a firmer, but still chewy, caramel, or take the caramel off the heat earlier for a softer caramel; 245 is perfect in my book).
Off the heat, stir in the vanilla without scraping down the sides of the pan - scraping the bottom of the pan is fine (this would be the time to add other flavorings/color).
Immediately pour the caramel mixture into the prepared pan. Let the caramels cool completely. I use a large, metal spatula to peel the whole slab of caramel out of the pan and onto a cutting board.
Cut into squares using a sharp knife or bench scraper, wrap, and store in an airtight container at cool room temperature for up to two weeks.
Vanilla: for a vanilla bean version, see this recipe.Double Batch: this recipe can be doubled (for a 9X13-inch pan of caramels). Use a larger pan so it doesn't boil over. A double batch will take longer to come to temperature at each step.Time: the exact time for each step will depend on how low or high you moderate the heat - as well as if you have a gas or electric stove.