In a medium saucepan and over medium heat, whisk together the condensed milk, brown sugar, butter, corn syrup, vanilla and salt. Continue to whisk until the sugar is dissolved and the mixture comes to a boil.
Attach a candy thermometer to the side of the pan and continuously whisk the caramel while it is gently boiling and until the temperature gets to 225°F. The sauce should be thick and golden brown which takes about 8-10 minutes.
Pour the caramel sauce over the warm crust. Do not scrape the sides and bottom of the pan. Cool for about 15 minutes or until the caramel is set.
To melt the chocolate, place it and the cream in a microwave bowl and heat just long enough that the chocolate begins to melt. Take it out and stir. The heated chocolate will usually melt the rest of the chocolate as you stir it. If you need to place back into the microwave, only heat for a few seconds at a time and take out and stir. Do not overheat the chocolate.
Stir well until smooth.
Spread the chocolate over the caramel layer.
Sprinkle the Maldon Salt on top of the chocolate. (Yes! This makes it very tasty!)
Refrigerate the bars for at least an hour to set the chocolate.
Using the parchment paper to lift the bars out of the pan and transfer to a cutting board.
Cut into small squares and serve.