Generously butter four 8-ounce or six 5-ounce souffle ramekins.
Put a couple of tablespoons of the sugar inside one ramekin and toss to coat, then tip the excess sugar into the next, and repeat until all the ramekins are sugar-coated.
Place the ramekins on a rimmed baking sheet.
In a large saucepan, add the milk and the vanilla bean and heat just to a boil over medium-high heat.
Turn off the heat, cover, and set aside to let the vanilla bean infuse for 10 minutes.
Remove the vanilla bean and rinse and reserve for another use.
To make the pastry cream, in a bowl, whisk 1/4 cup of the sugar with the egg yolks until thick and light, about 1 minute.
Whisk in the flour, cornstarch, and a pinch of salt.
Add a little of the warm infused milk and whisk to combine.
Add the remaining milk.
Return the egg mixture to the saucepan and bring to a boil over medium-high heat.
Decrease the heat to medium and cook, stirring constantly, until thickened, 45 to 60 seconds; it will be lumpy.
Remove it from the heat and whisk until smooth.
Set aside.
To beat the egg whites, in the bowl of a heavy-duty mixer fitted with the whisk, whip the egg whites with a pinch of salt on medium speed until foamy.
Increase the speed to high and beat until the whites begin to form soft peaks.
Slowly add the remaining 1/4 cup of sugar, beating until the whites are glossy and hold stiff peaks, 1 to 2 minutes.
Add about a quarter of the beaten egg whites to the pastry cream mixture and stir until well mixed.
Pour this mixture over the remaining whites and fold them together as lightly as possible.
To assemble the souffles, spoon the mixture into the prepared souffle ramekins (the mixture should come up to the top).
Smooth the tops with a metal spatula.
Run your thumb around the inside of the rim of each dish, making a shallow channel around the edge of the batter.
(This will help the souffles rise up straight and tall.)
Set the filled souffle ramekins on the rimmed baking sheet.
Bake the souffles until risen and just set, 12 to 15 minutes.
Remove from the oven.
With two forks, pull open the center of each souffle.
Place a scoop of vanilla ice cream in the opening.
Sprinkle with confectioners sugar and serve immediately.