Damp sugar with the cold milk in a large pan. Add the butter and condensed milk, turn heat to medium-high

I like to put a little dollop of uncooked mix onto a plate just to compare before amd after colour so that I know its done, I find looking is a better way of judging.

Keep stirring evenly until the mixture comes to a boil, this usually takes about 10 minutes. Watch the colour of the mixture, if you start getting caramel colour streaks turn the heat down a little, if you start getting black streaks you have burnt it. Good luck cleaning that up :)

Once the mixture boils turn the heat down low, stirring occasionally to prevent the mixture sticking. When simmering the mixture can get up to twice its original size so I hope you have chosen a big enough pan.

The mix should start to darken slightly so keep stirring now and then, it should take roughly 20 minutes to cook.

Put a little bit of the mixture onto a teaspoon and plunge it into a glass of cold water, it should form a small sticky ball that should drip off the spoon very slowly, when this happens the mixture is ready.

I personally like my Tablet a light colour so it is usually done about 18 minutes after being brought to the boil, if you would prefer a stronger flavour simmer for a little longer. Be careful though, dont over cook it.

Now for the difficult bit. Take the pan off the heat and start to vigorously stir the mixture, we're trying to get as much of the crystals from the side of the pan as we can. We want big enough crystals that it will set but small enough to still pour. This is of course much more difficult to describe than to do but when you feel the spoon start stirring grainily on the bottom of the pan it should be ready. You should be able to feel the difference.

Quickly pour the mix into the buttered tray and wait (preferably overnight) for it to set.

Do not be alarmed if you see weird patterns on top it is just the sugar crystallising as it cools.