1 cup whole milk
3 tablespoons rice flour (see note)
1/4 cup plus 2 teaspoons sugar
1 vanilla bean, split in half lengthwise, seeds scraped out
3/4 cup plus 2 tablespoons heavy cream
3/4 pound strawberries, cut into 1/8-inch cubes
Puffed rice cereal, for garnish
In a small bowl, whisk together 1/4 cup milk and flour.
In a small saucepan, combine remaining 3/4 cup milk, sugar, vanilla bean and seeds. Over medium heat, whisking frequently, bring mixture to a simmer, about 3 minutes. Immediately whisk in rice flour mixture, then, whisking constantly, allow mixture to come to a boil; cook, whisking, until thickened, about 2 minutes more. Transfer mixture to a large bowl; put bowl on a wire rack and let mixture cool, about 20 minutes.
In the bowl of an electric mixer fitted with the whisk attachment, beat cream on medium speed until stiff peaks form, about 8 minutes. Remove and discard vanilla bean from cooled rice flour mixture; whisk in 1/4 of the whipped cream. Repeat once. In 2 additions, using a rubber spatula, gently fold in remaining cream. Refrigerate mousse until chilled, about 45 minutes or up to 4 hours.
To serve, spoon mousse into serving bowls; top with strawberries and a sprinkle of cereal.
NOTE: Rice flour can be found at some large supermarkets, specialty grocers and health food stores.