Grease a slice tin (approx 28 x 18cm) and line with baking paper, leaving paper overhanging at sides to assist with removal of the tablet later.
Add all ingredients apart from the vanilla essence in a large saucepan. Mix to combine and then put on stove over low heat.
Stir until the sugar is dissolved, turning the heat up to low-medium if necessary.
Slowly bring the mixture to the boil and then boil for 10-15 minutes, stirring from time to time and turning down the heat if necessary to maintain a fast, steady boil.
If you have a sugar thermometer, take the mixture off the heat when the temperature of the mixture reaches 120 degrees celsius (248 degrees fahrenheit). Otherwise, watch the mixture as it changes to a more golden colour around the 8-10 minute mark.
Once you've take the mixture off the heat, stir in the vanilla extract.
Now, get ready cause this is the hard part. Stir the mixture vigorously for 10-15 minutes or until it thickens so much you can hardly continue to stir it.
If the mixture becomes smooth after you stop stirring for a few seconds, keep going. You want it to hold its shape when you stop stirring.
Pour the mixture into the slice tin and spread out evenly with a spatula, smoothing the top as best you can.
Allow to set for at least 6 hours, preferably overnight.
Ease the entire slab from the tin using the baking paper once set and then cut into small squares.
Notes
Storing: Scottish Tablet is best stored in something that is not completely airtight, for example a cookie jar or tin. It should last for up to 2 weeks given the sugar acts as a preserver.Freezing: You can also freeze Scottish Tablet for up to a few months. Wrap well before freezing. Thaw completely before eating.Nutrition: The nutrition information is an automatically generated estimate and is not guaranteed to be accurate.Tips and troubleshooting:
If your Scottish Tablet tastes sugary and grainy, or doesn't set, you can pop it back in the saucepan, melt it down slowly and boil it a little longer.
If the recipe doesn't work as expected, it's most likely because you're bringing the mixture to the boil too fast and not dissolving the sugar properly first (in which case, slow down) or it's not reaching setting point (in which case buying a sugar thermometer might help).
Some people suggest using an electric mixer to beat the tablet mixture and say it is successful. I haven't tried this. I personally like to burn off a few calories before I even eat this stuff. Remember, there's a whole kilo of sugar in there!