Heat the milk, cream and vanilla powder in a saucepan over a medium heat to just below boiling point, stirring often to make sure that the vanilla powder dissolves. Remove from the heat and leave to cool.

Whisk the egg yolks and caster sugar together until thick and pale. Pour in the warmed milk mixture, whisking all the time.

Return the mixture to the pan and cook over a very low heat for a few minutes, stirring continuously, until smooth and thick enough to coat the back of a spoon.

Remove the pan from the heat and pass the custard through a sieve into a clean bowl, then leave to cool.

Pour the strained custard into an ice-cream machine and churn for 20-25 minutes, until it is soft set. Just before the ice cream is ready, add the caramelized walnuts.

For the caramelized walnuts:

Heat the caster sugar in a saucepan over a medium heat until it melts to a golden caramel, swirling the pan from time to time (warning - do NOT stir, no matter how tempting it is).

Add the walnuts and move them around to coat them in the syrup, then pour the walnuts and caramel into a baking tin (ideally onto a silicon mat). Sprinkle generously with salt. Cover with another silicone mat then, with a rolling pin, roll out the toffee-like mixture flat. Leave to cool and set hard, then peel off the mat and roughly chop the praline into pieces that suit you for inside the ice cream.