For the soufflé base, whisk together the egg yolks and 50g sugar in a large bowl until thick and creamy.
Meanwhile, heat the milk and vanilla pods together in a pan until boiling. Whisk the flours into the egg mixture before adding the milk, whisking as you pour. Remove the vanilla pods. Pour this mixture into a large saucepan and stir over a gentle heat until thickened. Stir in the crumbled Christmas pudding and leave to cool – this can be done the day before and stored in the refrigerator until you are ready to cook the dish.
To make the soufflés, preheat the oven to 240°C/gas 8. Line eight 8cm ramekins by brushing lightly with butter. Chill for 5 minutes. Brush with more butter, then dust evenly with the remaining caster sugar.
In a large bowl, whisk the egg whites to form soft peaks. Measure out half of the Christmas-pudding base mixture and beat in half the whisked egg whites, then fold in the remainder of both mixtures. Spoon into the ramekins, smooth the tops with a knife and cook for 7–8 minutes until risen.
Dust with icing sugar and serve with ice cream.