Commercial fudge recipes

In Scotland we make a kind of fudge that is deliberatly hard and crystallised known as Tablet. This was a popular treat when I was growing up. Essencially the recipe for tablet, soft fudge, toffee and caramel are quite similar. The difference is made by how you cook and treat the mix as it cools.

Essentially you need to know about sugar boiling points. There are two important levels used: soft boil, and hard boil. My cook books suggest using a sugar thermometer to get the perfect boil but I've never found a sugar thermometer in the shops. Instead I rely on a great deal of practice, the colour, the texture and the drip of the mix to gage how hot the sugar is.

In a soft ball (234–240 °F or 112–115 °C), if you drip the mix onto a very cold surface or into cold water, then touch the drip with your finger, it will be soft like caramel. Additionally the colour will change from cream to yellow/tan.

In a hard ball (250–266 °F or 121–130 °C), dripping again onto a cold surface or into cold water, then touching the drip with your finger, it will be firmer or even hard. The colour will darken slightly to a dark yellow or light brown.

For caramel and fudge you go to a soft boil then cool. For tablet and toffee you go to a hard boil.

The next part is the cooling. This is equally important as the boiling. The faster you cool the mix the smaller the crystals become. The slower, the larger. If you want a caramel or a toffee, you must avoid agitating the mix as it cools. For fudge you should stir the gently as it cools slightly before pouring onto the try. For tablet, the mix should be vigorously stirred until stiff then poured onto a try.

The most likely culprit is how well you beat the mixture just before pouring it into the pan. I really like Alton Brown's explanation of the fudge-making process. What you're trying to do is form very small sugar crystals which provide fudge with its fine texture. Those crunchy bits you describe are larger crystal formations which can happen if you have a "seed crystal" remaining in the fudge as it sets. The purpose of stirring the fudge very well before pouring it into the pan is to deliberately form small crystals and break up any larger ones. If you didn't really thoroughly stir even just a few small patches of the fudge, some seed crystals may have developed there.

The clumps you describe in the initial mixture should have dissolved, but working them out would make sure that everything is evenly distributed. You can add the butter to the original mixture for the same reason instead of waiting until the end like the linked recipe recommends. A little bit of corn syrup will help control crystals too. Lastly, stir the fudge like crazy and scrape down as much of the work bowl as you can while you go. If your arms don't feel like they're about to fall off afterwards, you probably should have mixed it more.

Regarding temperature, remember that when simmering your fudge will carry over a couple degrees even after you turn off the heat. So you can kill the burner when your thermometer reaches 235F and monitor until you hit the target temp of 238F.

Quite honestly, fudge-making is a pretty sensitive process, so don't be too broken up if it takes a few tries and a lot of attention to detail before it's perfect.