First things first, make the espresso and set aside and allow to cool.
Bring a pot of boiling water (at least 5 cups) and then add boba (tapioca pearls), stir every so often. Boil for 5 minutes. Turn off heat and allow the boba to sit in the pot for about 10 minutes.
While you're bringing the water to a boil, in a smaller separate pot, add sugar (you can use a mix or all light brown sugar) and 1 cup of water. Bring to a boil and allow to boil for 5 minutes, until reduced. Mix every so often.
Using a slotted spoon, add the cooked boba to the sugar water and allow to sit for at least 10 minutes.
Add boba to two glasses.
Add espresso to a measuring cup and add enough water to make 1 1/2 cups. Add sweetened condensed milk and mix thoroughly. Add to blender with ice and blend until smooth.
Pour coffee smoothie over boba and serve with boba straws.
Tips: Unfortunately, cooked boba does not keep well in the refrigerator, it's best to serve it the same day you make it.
Boba instructions modified from Food52. Smoothie Recipe from the little kitchen.