To make the ice cream, split the vanilla pod in half and scoop the seeds into a pot along with the pod and the cream, bring everything to just under the boil.
Whisk the egg yolks and sugar until pale and thick. Pour the hot cream over them, whisking all the time.
Sieve this mixture back into the pot and cook on a low heat until the mixture coats the back of a spoon, stir constantly.
Leave to cook and churn in an ice cream machine until thick.
Pre-heat oven to 200ºC (Gas 7).
Break the chocolate into small pieces and place in a bowl with the butter and half the caster sugar over a pot of simmering water, leave until everything Is melted, then stir until all ingredients combined.
Put the eggs and the remaining sugar in a food processor and blend for about 10 minutes - the mixture will have more than doubled in size and be very thick and pale.
Transfer to a large bowl and gradually fold in the flour and then the cooled melted chocolate mixture (if the mixture ‘splits’ at this point, add a little water and it will emulsify again).
When ready the mixture will be quite runny, at this point, pour it into a buttered 20-cm Springform cake tin (with a removeable base) and bake in the oven for 6 minutes, the rim will be cooked while the centre appears liquid.
Leave the cake to cool and cover and leave in a cool place (not the fridge) It is best to leave this cake set overnight.
To serve, cut a slice of cake and dust with cocoa powder and garnish with ice cream scoop and some fresh raspberries.