Place all the batter ingredients except iced water and butter into the Thermomix bowl and blend on 20 sec/speed 8. Allow to rest while you preheat the oven.
Place a cast iron frying pan with a dollop of butter into the oven and preheat to 220°C fan forced.
When the pan and oven are heated, add the iced water to the batter and blend until well mixed. Working as quickly as possible, to preserve the heat of the oven and pan, pour enough batter into the frying pan to cover the base completely. Return to the oven for 15 minutes until puffed and golden
Stir the creme fraiche and 1 tsp of the vanilla together in a small bowl. Set aside.
Remove the pancake from the oven, spread a few tablespoons of the vanilla creme fraiche mixture on the pancake. Top with berries and dust with icing sugar. Serve immediately.
To slow roast the berries, place them into a shallow baking dish with the remaining vanilla and champagne. Cook in a 160°C oven for 10-15 minutes before topping the Dutch Baby with them as described. These can be pre-made up to a week in advance.