Swiped the following from
http://www.craftbrewer.org/.
Now, how to make it. Well you need a good high temperature thermometer. Mercury thermometers that go up to 350° C will be very accurate, but are clumsy to use, and can easily break as you plunge them in and out of a hot sugar solution. Spilt mercury is not something you really want to have to deal with. Still they do work. But I have found the proper candy thermometers that clip on the side of the pot are ideal. You get them from kitchen supply shops and they cost only about $10.00.
Now any good cook will tell you there are certain temps you boil sugar water at for different lollies. Basically, this is the temperature that the boiling syrup will reach as the water evaporates concentrating the sugar and hence raising the boiling point of the solution.
So let's say you want to make 500 grams of candy sugar. You weigh 500 g of white sugar and into a small pot. Add enough water to make thick syrup. Add a pinch of citric acid (I will explain why later). Now bring to a boil and keep the temperature between hard ball and soft crack (127-135°C). As evaporation will cause the temperature to rise, have a small amount of water and add a tablespoon every now and then.
The colour will gradually change from clear to light amber to deep red as the boil proceeds. Light candy sugar is a very light pee colour (yes, that type of pee). This can take only 15 minutes. Dark candy sugar is very deep red. This can take hours. Once you are at the colour you desire (and a lot of that is on taste), you let the temp go to hard crack (150°C). Once it hits hard crack, turn off the heat and pour it into some greaseproof paper. As it cools it will go rock hard. I then put it in the freezer until I'm ready to use it.
Now why add citric acid? This is to 'invert' some of the sugar. Simply put, cane sugar (sucrose) is made up of two other sugars (glucose and fructose) joined together. Yeast must spend time and effort breaking the joining bonds to allow them to get at the simple sugars they need for metabolism. This can also be done chemically in an acid environment with heat. The citric acid supplies the acid, and the heat is there when you make the candy sugar. Invert sugar tastes a bit sweeter than regular sucrose. This is all just so easy there is no reason not to give it a try. It will make your Belgian beers really special.
Cheers,
Greg