Melba's Peanut Butter Fudge

From Grandma Joy: I hear the ingredients in a regular baking pan. I like to cook it on high. It is cooked to a soft ball stage. I now use a food thermometer to get that a little closer to the soft ball stage instead of guessing like Melba did. Then I cool it down, about 5 minutes usually does that in cold water. I take it out of the water, spoon the peanut butter into the cooked ingredients and beat it in. It takes about 2 minutes to maybe 5 or a little more before it starts to thicken and set up. This recipe takes a little practice to get just right so don't give up. It is a precious recipe that Melba's mother used to make.