I was given a fudge recipe citing evaporated milk instead of sweetened condensed milk. Is it possible to fix this by adding sugar and re-cooking the fudge or is it just a recipe gone bad?
Add 1 to 1/4 cups of sugar for each cup of evaporated milk. Put it on top of a stove and stir until the sugar is dissolved. If the state of your recipe is such that you cannot put it on top of a stove then use icing sugar instead and mix until the sugar is completely incorporated.
Along with any sugar you added, you might want to add some cream of tartar. About 1/4 to 1/2 tsp would be enough for a can or two of evaporated milk. Start with the smaller amount, though.
It's a thickening/solidifying agent. Good for use in icings and such. I've messed around with it in a few recipes for replacement, just in case I make a mistake or don't have something on hand. It works well when I put it into a very enriched batter that I would like to either slightly stiffen or thicken. Especially well when used with sugar (usually I use 10x).