Grease a 9x13" baking pan and line with parchment that overhangs sides. In metal bowl or double boiler, add all ingredients except salt. Set over pot of gently simmering water, stirring constantly until chocolate has completely melted - mixture will be very thick. Pour into prepared pan. Allow to cool to room temperature then cut into squares. Sprinkle a few grains of sea salt on each square.
Makes about 3 pounds of fudge.