Pour the milk into a heavy-based saucepan and heat until just beginning to simmer.

Beat egg yolks until pale and fluffy, and thickened.

Slowly pour hot milk onto beaten eggs, still whisking. Set aside.

Combine sugar and water in a saucepan, and stir over a low heat until sugar has dissolved

Increase heat to medium-high, brush down any sugar crystals on the sides of the pan, and cook without stirring until the mix darkens and becomes a caramel syrup.

Remove from heat and pour in cream. Mix well.

Return mixture to a low heat and stir to dissolve any lumps of sugar. Add the egg mixture, then the salt, and stir constantly until it thickens, and coats the back of a wooden spoon.

Pour the mixture into a heatproof bowl, cool, then cover and chill until cold.

Once chilled, pour into the ice-cream maker, set to ice-cream setting, and churn.

As the mixture thickens, towards the end of the cycle, add the Twix Mix.