Yes, you can over beat fudge. There is a slim window during the beating process when your fudge will be absolutely perfect. Once you have reached this stage, you will need to stop beating it immediately. This is because if you start to over beat your fudge, it will become rock hard and unworkable. You should only beat your fudge until it starts to lose its shine, and the mixture starts to thicken up. Once it has lost that glossy appearance, it’s time to stop beating your fudge, and then turn it out into your prepared pan so that you can leave it to set.