Preheat oven to 375 degrees F.
Butter an 8 by 11-inch oval baking dish. Spread blueberries on the bottom of the baking dish.
Combine the milk and vanilla bean in a small saucepan. Bring almost to a boil. Remove from heat. When milk has cooled slightly but is still warm add the cream and sour cream. Stir well.
Make custard by whisking together eggs, egg yolk and sugar until well blended. Whisk in the flour and salt. While whisking gently pour milk/cream mixture over egg mixture. Blend well.
Pour custard through a sieve over the blueberries into the baking dish. Bake for 30 to 35 minutes or until custard is set and puffy. Let cool slightly but serve warm. Sprinkle with icing sugar before serving.