If you have all the ingredients for key lime fudge apart from this one, don't worry because you can turn evaporated milk into condensed milk. Combine a 12-ounce can of evaporated milk with 1½ cups of white sugar in a pan. Bring it to a boil over a moderate heat, stirring all the time. When the sugar has dissolved and the mixture is a little thick, let it cool then proceed with the recipe. This recipe makes the equivalent of a 14-ounce can of sweetened condensed milk.