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.
**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.**
Cook time refers to chilling time