1 kilo/2.2lbs granulated sugar
Large tin condensed milk - 397gms/14oz
1 cup of milk
vanilla extract about 1 teaspoon (optional)
Put all but the condensed milk in a heavy bottomed pan, and melt really slowly until there are absolutely no grains of sugar left,
Avoid stirring it vigorously, as you will push grains of sugar up the side of your pan and have gritty tablet.
If you do get grains up the side of the pan sweep them down with a wet silicone pastry brush.
Once it is all melted add the condensed milk and take to a rolling boil,
Now this varies as to how long it takes. It will change colour to a toffee colour but not too dark.
Test a drop of the mixture in a glass of cold water it should form a ball when rubbed between your fingers. If you have a sugar thermometer approx 240.F/12o.C .
Take it off the heat and beat it really well with a wooden spoon, you will feel it thicken as you beat, then pour into 8x10 inch greased swiss roll tin and leave to set.
Mark it before it is totally cold.