How to Make It
In a bowl, soak the fruits in the kirsch for 30 minutes or overnight. Preheat the oven to 400°. Grease a 1-quart soufflé dish with butter and dust with 2 tablespoons of the sugar; refrigerate. In a saucepan, melt the 3 tablespoons of butter over moderate heat. Whisk in the flour to form a paste and cook, whisking, for 1 minute. Whisk in the milk, bring to a boil and cook, whisking constantly, until thickened, 1 minute. Remove the béchamel from the heat, then whisk in the vanilla and remaining 1/3 cup of sugar. Whisk in 4 egg yolks; reserve the remaining yolk for another use.
In a clean bowl, beat the whites until firm peaks form; whisk one-third into the béchamel, then fold in the remaining whites. Fold in the fruit and kirsch; scrape into the dish. Bake for 25 minutes, until puffed and lightly golden. Dust with confectioners' sugar and serve.