1 Cup butter
1 16-oz package (2-1/4 Cups packed) brown sugar
1 Cup light corn syrup
1 14-oz can sweetened condensed milk
1 tsp Vanilla Extract
Using butter (not nonstick spray), generously grease a 9×9-inch baking pan.
Melt the butter in a heavy 3 qt saucepan, over low heat on the stove. When butter is melted, stir in brown sugar and a dash of salt. Add in corn syrup, then mix sweetened condensed milk into mixture, a little at a time.
As mixture heats over medium heat, stir constantly, to 245F (firm ball stage), maintain this temperature for 20 minutes.
Remove mixture from heat, stir in vanilla, then pour into buttered pan. Allow to cool at least six hours before cutting into squares with a sharp wet knife.
Dip square caramels in melted dark chocolate and sprinkle with sea salt or sanding sugar, if desired.