Preheat oven to 350 degrees. Spray or line a 9×9 pan. In mixer, cream the butter, add sugar and vanilla and beat util fluffy. Add egg and flour until combined. Transfer to prepared pan and press into a even layer. Bake for 22 minutes or until golden brown. While this is baking, combine caramel ingredients in sauce pan, over medium heat whisk continuously until it bubbles and turns a rich color, about 225 degrees. Pour over the shortbread base and smooth out over the crust. Chill for 10 minutes until caramel sets. In a microwave bowl, combine the chocolate chips and heavy cream. Microwave at 30 second intervals until melted, pour over the caramel layer, smooth and then sprinkle with sea salt. I placed it back in the cooler before I cut them as I found it easier to cut when they are cool.