For the caramel
250g/8oz caster sugar
125ml/4fl oz water
250ml/8fl oz water to finish
A pinch of sea salt
For the panna cotta
250ml/8fl oz double cream
185ml/61/2fl oz whole milk
1 vanilla pod, split lengthwise
100g/31/2oz caster sugar
2 sheets of medium-strength gelatine or 11/2 teaspoons of powdered gelatine
4 blood oranges
Start by making the caramel. Place the sugar and 125ml of water into a small pan. Place over a low heat to dissolve the sugar, stirring with a wooden spoon for a minute.
Once the sugar has dissolved turn the heat to high and cook without stirring until it is a rich dark caramel. Remove from the heat and immediately pour in the second lot of water.
Add the salt and return to the stove and cook over a low heat, stirring with a wooden spoon for a minute or so. Remove from the heat and allow to cool.
Now place the cream, milk, vanilla pod and sugar into a heavy pan over a low heat and bring to a gentle simmer. Stir to help dissolve the sugar. Remove from the heat, and set aside to infuse for 20 minutes.
In the meantime immerse the gelatine sheets in a bowl of cold water and leave to soften for five minutes. If using powdered gelatine, follow the on-pack instructions.
Return the infused mixture to the stove over a low heat to warm through. Remove the gelatine from the water, squeezing out any excess, then add to the warm cream. Stir to dissolve. Strain into a jug and pour into four dariole moulds and allow to cool to room temperature. Place in the fridge for at least two hours.
To serve, dip each mould into warm water for a second or two to loosen the edges, then invert on to a plate.
Remove the skin from the oranges, slice into pin wheels and arrange round the panna cotta. Spoon over the caramel and serve.