Caramels are one of the easiest and (yes) fool-proof candies you can make.
Line an 8x8 baking dish with parchment so that excess paper hangs over the edges. Spray the parchment and the sides of the pan with nonstick spray.
Over medium heat, warm the cream, butter, and salt in the 2-quart saucepan until the butter melts. Remove from heat, but keep the pan close by.
In the larger 4-quart saucepan, combine the sugar, corn syrup, and water. Stir until the sugar is evenly moistened and you form a thick grainy paste.
Wipe down the sides of the pan with a damp pastry brush so there are no sugar crystals above the surface of the sugar mixture.
Clip the instant-read thermometer to the side of the pan.
Place the pot with the sugar mixture over medium to medium-high heat. Do not stir. At first, you will see small bubbles around the edge of the pan.
The small bubbles will eventually move inward.
Around 250°F, the sugar syrup will turn transparent and boil rapidly.
Around 320°F, the syrup will darken slightly and smell caramel-like. You can proceed to the next step any time after the syrup reaches 250°F and before it reaches 325°F.
If your instant-read thermometer isn't quite submerged into the sugar, you may need to tilt the pan to get an accurate reading.
Turn off the heat under the sugar syrup. Slowly pour the warm cream and butter mixture into the sugar syrup while whisking the sugar syrup gently. The sugar syrup will bubble up and triple in size.
Return the pan to medium to medium-high heat. Let the caramel come to a boil without stirring. It will start off as a soft buttery yellow.
The caramel will eventually darken to a brown caramel color. Remove from heat when the caramel reaches 245° to 250°F.
Quickly whisk the vanilla into the caramel.
Immediately pour the caramels into the mold. Do not scrape the pan (there are sometimes hard burnt bits on the bottom).
Set the caramels somewhere out of the way to set, for at least two hours or (ideally) overnight.
Cut the caramels into candies with a very sharp knife.
Cut squares of wax paper a little longer than your caramels. Wrap each caramel in wax paper and twist the ends closed.
Caramels will keep at room temperature for about two weeks.