How to add ingredients to fudge without stiring it

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.

I like Kristina's suggestion that you research some of the basics of candy making. I'll answer those questions only briefly.

Generic Candy Questions

• You don't need to heat particularly slowly
  This is not like an egg custard where the speed of heating will affect the curdling temperature. You're just trying to get water out. Just don't heat it so fast that you burn the bottom or overshoot the target temp.
• Temperature range
  The different candy stages have about a 10F range. 2-5 degrees isn't going to make much of a difference but 7-12 will start to.
• Adding volatile flavorings to candy
  Many flavorings are lost to heat. Such flavorings are added at the end because if they boiled the entire time they would be gone.

Fudgy questions

• Stirring
  Stirring isn't required. The syrup won't burn unless you have the heat too high and are using a very cheap pot. Additionally, the syrup absolutely should not be stirred in the final moments of boiling because a sugar crystal might fall in that doesn't get dissolved. During cooling stirring would destroy the fudge because it would all crystallize.
• Drying out
  This is not a problem. The fudge will not dry out in the time it takes to cool.

• Losing the gloss
  As I wrote in the other answer, the syrup is concentrated and then cooled to a super saturated state and not allowed to crystallize. When it has cooled sufficiently it is mixed like crazy to form your crystals all at once. When this happens the shiny, glossy syrup suddenly fills with crystals and becomes thick and loses the gloss.

  It is important that the syrup be cooled enough that it is ready to crystallize at the drop of a hat. Again- if you stir it early, as it cools, you will end up with rock candy (more or less). I just leave my candy thermometer clipped on until the target temperature is reached. Make sure the thermometer is clean- one stray sugar crystal can ruin the batch.