Bring to a boil and boil for 5 minutes, stirring frequently. Attach a candy thermometer to the side of the pan. Maintain a medium boil, stirring frequently until the mixture reaches 240˚F. This will take 8-14 minutes, depending on the heat.
See Café Tips above in post for lots of extra tips and instructions as well as method to make this fudge in an 8x8-inch square pan.