In a medium pot, bring 6 cups of water to a boil. Once boiling, pour in tapioca pearls. Immediately give it a stir to prevent clumping at the bottom of the pot.
Boil uncovered for 15 minutes, stirring occasionally. Remove from heat, cover, and let sit for another 15 minutes.
Drain away the water and transfer cooked tapioca pearls to a small bowl. Add in brown sugar while the pearls are still warm and stir to dissolve sugar into a syrup. Add a spoonful of water if it’s too dry. Set aside.
In a blender, add in the flesh of the avocado, milk, condensed milk, and ice. Blend until smooth and creamy.
In a tall glass, spoon in about 100g of tapioca pearls with brown sugar syrup. Fill the rest of the glass with the avocado smoothie. Stir well before enjoying with a large boba straw.