In a small bowl, soak 1 cup small tapioca pearls in one can of coconut milk. Stir and let sit on the kitchen counter for 3 hours (no need to refrigerate), stirring occasionally.
After letting the tapioca soak, pour it into a medium saucepan. Add to the tapioca mixture, 2 cups of milk, ¾ cup sugar, salt, and egg yolk. Heat on medium heat, stirring frequently to keep milk from scalding. Once the tapioca mixture is simmering (do not boil), turn down the heat to medium-low and simmer for 10 to 15 minutes, stirring constantly to keep milk from scalding.
Carefully taste-test the tapioca to be sure the pearls are soft and no longer chewy. If the tapioca pearls are still chewy, cook for an additional 5 minutes and check again. When the tapioca is done, remove it from the heat and let it cool for 15 minutes.
While the tapioca is cooling, beat the egg whites with 1 tablespoon sugar until stiff peaks form.
Stir the coconut extract into the tapioca and gently fold in the egg whites until completely incorporated.
Serve warm or chilled for 4 hours in the refrigerator. To serve, divide tapioca into individual bowls and top with fresh mango or fresh fruit of your choice. Garnish with toasted coconut or shredded chocolate (optional).