- In a saucepan, pour the milk. Add the tapioca, vanilla, egg yolk, and salt. Stir well with a whisk. Let rest for 5 minutes.
- Bring to a boil over low heat, stirring constantly with a spatula, scraping the bottom and sides of the pan. Simmer very gently for about 15 minutes, stirring frequently or until the tapioca becomes translucent. Transfer to a large bowl. Set aside while preparing the maple mousse.
- In a tall saucepan, cook the syrup over medium heat until it thickens or until a candy thermometer reads 115 °C (240 °F) (you will end up with about 180 ml / 3/4 cup).
- Meanwhile, in a bowl, beat the egg whites with an electric mixer until soft peaks form. Drizzle the hot syrup over the eggs, being careful to avoid the beaters. Beat continuously until the meringue is just warm and stiff peaks form.
- With a spatula, fold the maple mousse in the tapioca. Serve warm or cold.