Seriously. These are THE BEST. I found this recipe at bakingbites.com after trying a few others with no success. The recipe is easy to follow. I add a bit of vanilla to the heavy cream, and some chopped pecans to the caramel.
I line a 9x12 pan with parchment paper and sprinkle some chopped pecans on the bottom. After the caramel solution hits ~245-250, I immediately pour it into the pan. I set the pan in the fridge for 10 minutes.
After 10 minutes I remove the pan and sprinkle on some fleur de sel (chunky/flaky salt). After a few more minutes in the fridge, I remove the parchment from the pan and put the parchment/caramel sheet back into the fridge for 20 more minutes. Then I use a hot knife to cut it into strips then squares.