1. In a medium saucepan bring 4 cups of water to a boil. Add tapioca pearls then reduce heat to simmer for 15 minutes, stirring occasionally. Take off heat and let sit for 15 minutes more. 2. In a medium saucepan bring milk to a gentle simmer. Add tea bags, cover, and let steep for 10 minutes. Remove tea bags. 3. Pour tea-infused milk into a blender and add ube jam, vanilla, and optional ube extract. 4. Blend until smooth. 5. Strain and rinse tapioca pearls and divide them among 4 tall glasses. Fill glasses with ice cubes, and pour ube-milk mixture over the ice. Serve immediately with boba tea straws or long spoons.