1 cup (8 oz, 240 ml) whole milk
1 vanilla bean, split
1/2 cup (4 oz, 112g) granulated sugar, divided
2 tablespoons (1/2 oz, 14g) corn starch
4 large egg yolks
1 cup (8 oz, 240 ml) heavy cream
2 tablespoons wate
1 1/2 teaspoons plain gelatin powder
2 large egg whites
1. Place the the milk in a pot over medium high heat. Scrape the seeds from the vanilla bean and add them to the milk along with the pod. Heat until the milk is scalding hot, but not boiling.
2. Remove 2 tablespoons of the granulated sugar and set it aside.
3. While the milk heats up, whisk together the rest of the sugar with the corn starch and egg yolks. Whisk the hot milk into the egg yolks, then return the mix to the heat. Cook the custard over low heat, stirring constantly, until the mixture just begins to boil and thickens. Remove from the heat and strain into a clean bowl. Discard the vanilla pod or rinse it and set in a bin of sugar to make vanilla sugar.
4. Refrigerate the custard for at least 2 hours (must be completely cooled) before continuing with the recipe. To speed up cooling, set the bowl of custard over a bowl of ice water and stir until cooled.
5. Whip the cream to soft peak and fold it into the chilled custard base. Return the bowl to the refrigerator while you prepare the other ingredients.
6. Place the water into a microwave safe bowl. Sprinkle the gelatin in an even layer over the water and set it aside to bloom.
7. Combine the egg whites with the reserved 2 tablespoons of sugar in a heatproof mixing bowl. Set the bowl over the pan of almost simmering water (don't allow the bottom of the bowl to touch the water) and heat to 160°F, stirring constantly. Remove the whites from the heat and whip until they are at full peak and completely cooled.
8. Heat the bloomed gelatin in the microwave in 10 second increments until it's hot to the touch. Working quickly, add a 1/2 cup of the mousse to the warmed gelatin. Whisk to combine. Pour the gelatin mixture back into the mousse. Immediately whisk until the mousse is smooth and the gelatin is evenly incorporated. Immediately fold the whites into the mousse.
9. Pipe or spoon the mousse into serving glasses while it's is still soft. Refrigerate until set.
10. Serve with fresh berries, fruit sauce or chocolate shavings.