Grease the square baking pan and line the whole thing with parchment paper. Leave enough excess to be able to lift the set caramels out of the pan.
In the pot, combine all ingredients except for the salt and vanilla extract.
Heat over medium-high until the mixture is completely melted and starts to simmer.
Attach your candy thermometer if you haven’t already, and stir continuously until the mixture reaches 240 degrees - around 20-30 minutes.
Remove pot from heat, but continue stirring so the caramel does not scorch. Add in salt and vanilla extract and stir until combined.
Pour caramel into your lined baking dish and allow to sit at room temperature until solid enough to cut. For soft caramels this will probably take a few hours, but for firmer caramels it may only take minutes. You may chill in the refrigerator if needed.
Once set, remove the caramel from your pan by lifting the excess parchment paper. Use a knife, bench scraper, pizza cutter, or other such tool to cut your caramels however you’d like.
Wrap in wax paper or candy wrappers to keep them from sticking together. Stored in an airtight container, these caramels will keep for several weeks or for several months in the refrigerator or freezer.