In a bowl, mix 1 cup of tapioca starch and 2 tbsp cocoa powder. Mix until well incorporated. Set aside.
In a sauce pan, put 2/4 cup of brown sugar, 1/8 cup tapioca starch, and 1/2 cup water. Stir until starch and sugar are dissolved. Put over low fire. Stir constantly until the mixture becomes sticky.
Turn off heat and add the dry mixture (tapioca starch and cocoa powder). Mix.
Pour over the combined mixtures over a working table and knead the dough while slightly hot. Knead until it becomes smooth and form into a big ball.
Cut into 4 parts. Roll each part into long logs. Once rolled, cut them into 0.5 cm small pieces.
Shape the small pieces into small balls. Cover other pieces to prevent them from hardening. The dough will quickly harden when exposed to air, so you should cover them with cling wrap. Sprinkle some tapioca starch over the small balls/pearls to prevent them from sticking together.
Fill water in a sauce pan and bring it to a boil. Once boiling, put the pearls into the boiling water. Cover and let it boil again over high heat for 20 minutes. Lessen the heat and let the pearls cook for another 10 minutes. Turn off the heat but keep the sauce pan covered for 30 minutes more. This will allow the pearls to cook slower without the pressure of fire.
After 30 minutes, drain out the water from the pearls.
In a different sauce pan, dissolve 1/4 cup of brown sugar, the remaining tapioca starch in 4 tablespoons of water. Add in the cooked pearls. Cook over low heat until the mixture becomes sticky.
Turn off the heat, prepare your favorite milk shake or tea and add up your homemade pearls!