The night before making your tapioca, soak the small tapioca pearls in 1 cup cold water. You can also do this 6-8 hours before. Drain well and set aside.
In a medium saucepan combine milk, 2 tablespoons of the sugar, salt and tapioca. Bring to a boil over medium heat stirring constantly. Once the mixture boils, lower the heat and cook for 3-5 minutes or until the pudding thickens and the tapioca pearls are soft and clear.
Separate the egg and reserve white in a small mixing bowl. Add some of the hot tapioca mixture into the yolk and whisk well. Repeat a couple of more times until the egg yolk is tempered, then return back into the hot pudding. Whisk vigorously until smooth and return to heat.
Cook pudding for another minute and remove from heat. Add vanilla and stir well. Beat the reserved egg white until soft peaks form. Slowly add in remaining 2 tablespoons of sugar. Beat until stiff peaks form.
While pudding is hot, fold in the whipped egg white. This will lighten the mixture and make it more airy. Serve pudding warm or chilled.
Notes
If you are using instant tapioca, you only need to soak it for 5 minutes. Proceed with the rest of the recipe as normal.