Line an 8 x 8 pan with parchment paper - do not skip this or you likely won't be able to get your fudge out looking very nice.
Combine the milk chocolate chips (or dark or semi-sweet) and the sweetened condensed milk in a microwave safe bowl. Stir together and microwave for 30 seconds then stir for 30 seconds. Microwave in bursts of 15 seconds stirring for 30 seconds in between until completely melted. Stir in the vanilla extract.
Pour into the prepared pan. Spray a spatula with nonstick cooking spray and smooth the chocolate fudge.
Quickly rinse out and dry the bowl. Combine the unwrapped caramels and heavy cream in the bowl. Microwave for 30 seconds then stir for 30 seconds. Return the mixture to the microwave and microwave in bursts of 15 seconds stirring for 30 seconds in between until completely melted.
Pour the caramel over the chocolate evenly.
**If you want a chocolate caramel swirl fudge, prepare the two layers at the same time (so they are both melted at the same time lay down the chocolate and then immediately (because it hardens quickly) pour the caramel over in vertical lines. Using a butter-knife swirl the layers together.**
If desired top the fudge pieces with sea salt.
Cover tightly and place in the fridge to harden/set up overnight.
Cut the fudge with a hot wet knife.
Store any leftover fudge in an airtight container in the fridge.