Lightly grease an 8 x 8-inch baking pan.
Line the pan with parchment paper, allowing the excess paper to overhang the sides, set aside.
In a large, heatproof bowl combine the sweetened condensed milk, vanilla extract, chocolate, and butter and set aside.
Fill a saucepan with a little water (about ¼ full) and bring it to a boil.
Reduce the heat to a simmer.
Place heatproof glass bowl on top of the pot.
Stir frequently, until the chocolate has melted and the mixture is completely smooth, about 8 minutes.
Remove from heat. The mixture will be very thick.
Using a sturdy spatula, scrape the fudge into the prepared pan and smooth the top. Sprinkle with sea salt.
Refrigerate for at least 2 hours.
Gently run a metal spatula around the edge of the pan to loosen the fudge.
Remove the fudge and transfer to a cutting board.
Gently remove the parchment paper and slice the fudge into small pieces.
If you are not serving immediately, store in the refrigerator.
This can also be frozen in an airtight freezer safe container for up to two months. Recipe inspired by BakerByNature
