Pre heat the oven to 180'C.
Cut the peaches in half and remove the stone and place them flat side up on a baking tray lined with greaseproof paper.
In a large saucepan, add the sugar and place onto a medium heat. Keep tilting the pan to move the sugar around to speed up the melting process. After 5 minutes the sugar should be turning into a caramel colour.
When the caramel is golden, remove it from the heat and add the butter. Using a spoon combine the butter with the sugar until all the butter has melted. When the butter has melted, add the white wine. Return the pan back onto the heat as the caramel will solidify when you add the cold wine. On a low heat, melt the sugar again until it is a smooth consistency, At this point, spoon the caramel onto the peaches until they are glazed with the caramel.
Place the peaches into the oven for 6 minutes. After six minutes, remove the peaches from the oven, tilt the tray so the juices run into one corner. Using a spoon, place the juices over the peaches and cook for a further 4 minutes until the peaches are just soft.
Fill a large saucepan half full with water and place it onto the heat.
Split the vanilla pod and scrape the seeds out.
Place the egg yolks, sugar, vanilla seeds and the cognac in a round bottomed metal bowl and place directly over the pan of simmering water (bain-marie).
Whisk the mixture continuously for 6-8 minutes. The mixture will become pale in colour and will thicken, resembling a custard. Remove from the heat once you reach this stage.
«Customise this recipe at will: you could use sherry or amaretto in the zabaglione, flavour it with orange or lemon zest, and serve it with fresh berries.»