- 800g/1lb 12oz caster sugar
- 200ml/7fl oz full-fat milk
- 125g/4½oz butter
- 397g tin condensed milk
- 1 tsp vanilla bean paste
Combine all of the ingredients, apart from the vanilla, in a large, deep saucepan. Put the pan over a medium heat and simmer, stirring often, until the mixture turns a dark caramel colour, about 30 minutes. Keep an eye on it, if it catches reduce the heat accordingly.
Add the vanilla bean paste and increase the heat to a boil. When it reaches 120C on a sugar thermometer, pour into a big bowl and leave to cool for a couple of minutes. Beat the mixture for about 10 minutes with a spatula or wooden spoon until grainy and it loses its shine. Spread the mixture evenly over a lined 40cm/15¾in baking tray and leave for at least 2 hours at room temperature or until completely cool.
Once completely cool and set, cut into squares to serve.