Lightly grease the bottom and sides of a 9-inch round pan.
In a medium saucepan, warm the condensed milk over medium heat for a few minutes. Then add the chocolate chips and begin stirring, scraping the bottom and sides of the saucepan as the chocolate melts. Continue stirring vigorously until the chocolate chips have melted and are fully incorporated.
Remove the pan from heat. Stir in the vanilla extract and fine sea salt until fully incorporated. The fudge should have a smooth, creamy consistency at this point.
Pour the fudge into the prepared pan. Use a rubber spatula to help spread it into an even layer.
Set the fudge in the refrigerator for at least 1 hour. After 1 hour, spoon caramel dip on top of the fudge. Use a rubber spatula to spread it into an even layer, almost like frosting a cake. Then sprinkle evenly with coarse sea salt.
Set the fudge in the fridge for at least another 2 hours, or overnight. This will help the caramel dip solidify slightly so that the fudge is easier to slice and serve.
To serve, carefully remove the fudge from the pan and smooth out the caramel around the edges with a knife or rubber spatula. Let it warm up at room temperature for at least 5 to 10 minutes, or run a knife under hot water to slice through the cold fudge.