I would like to make Hokey Pokey with our youth group of twelve year olds. Before I do, please could you andwer the following questions? How long does it take to set? I will have to do the whole thing from start to finish in about an hour and a half. What temperature should the mixture be at (so I can be sure I don't mess it up!)? What chemical process is taking place when it wooshes up, so I don't look an idiot for not knowing if they ask me?
Nigella's Hokey Pokey (from Nigella Express and on the Nigella website) sets quite quickly as the candy needs to cool to room temperature. The cooling time will depend on the warmth of your kitchen, but if you have a cool, dry place to let the Hokey Pokey cool then it should be possible to make it in 1 1/2 hours. Putting the baking sheet on a wire cooling rack is also a good idea. We would mention that hot sugar can cause nasty burns so make sure that the children are positioned at a suitable distance. Also the baking sheet that you pour the hot mixture onto can heat up, so should be handled with oven gloves until the candy has cooled sufficiently.
The sugar mixture should be boiled to 150-154c/300-310F. This is known as the "hard crack" stage as the sugar will form strands that crack when pressed. You can also drop a little of the hot sugar into a glass of cold water and you will see that it forms a brittle thread when it goes into the water. The mixture should not be stirred once it is boiling as this can cause the dissolved sugar to crystallize again and the Hokey Pokey will be grainy. Instead swirl the pan gently and only boil once all of the sugar has dissolved fully. When the bicarbonate of soda (baking soda) is added to the mixture it forms carbon dioxide bubbles and this causes the mixture to foam up. Bicarbonate of soda is alkaline and sugar is mildly acidic and when the two combine it casues this chemical reaction.