Heat 300ml cream, 300ml milk, and vanilla seeds in a saucepan until just below boiling.
Cool the mixture for one hour to infuse, then discard the vanilla pod.
Whisk egg yolks and 100g sugar until pale, then gradually whisk in the cream mixture.
Cook the custard over gentle heat until thickened, then chill in the fridge overnight.
Churn the custard in an ice cream machine until thick and freeze until needed.
Whisk egg whites and 175g sugar until glossy, stiff peaks form.
Spread jam on the cake, top with ice cream scoops, and cover entirely with meringue.
Freeze the assembled Alaska until ready to bake.
Bake in a preheated oven at 200°C for 8 to 10 minutes until golden.