Boil at least 1 cup of water in an electric kettle or saucepan. You won’t use all of it, but have extra hot water on hand in case the dough is dry.
If you are making dark brown pearls with molasses, pour 40 grams (2 tablespoons + 2 teaspoons) of hot water directly into the bowl with the starches. For all other types of boba, pour 45 grams (3 tablespoons) of hot water directly into the bowl with the flours. Once the hot water touches the starches, it will gelatinize some of the starch immediately, turning it into a translucent, gooey mass. This is very important for the dough to form properly. DO NOT pour and measure the hot water into a separate bowl before adding to the flours, as this significantly reduces the heat of the water. I generally place the bowl of flours on a scale and pour hot water from my kettle into the bowl, using the scale to measure the water. (See note 7) If you’re making the black boba, add the food coloring now.
Use a flexible spatula to fold and press the dry flour into the gelatinized starch, until a dough starts to form. Most of the moisture is in the center of the dough, so keep gathering and pressing dry flour into the center of the dough mass. Continue folding dry flour into the dough for another 1 to 2 minutes, until it looks like 80-90% of the flours have been incorporated into the dough.
Transfer the dough and any loose flour to a work surface and use your hands to finish kneading the dough. Work the dry flour into the dough by pressing and squeezing it into the dough. After a few minutes of kneading, you should get one cohesive piece of dough that’s moist but not sticky. The dough should be relatively smooth, but don’t worry if there are tiny clumps of flour in the dough.
If the dough is very dry and crumbly, gather all the dry flour. Drizzle a teaspoon of hot water over the loose flour and work the flour into the dough. Conversely, if the dough is feeling sticky (this can be the case when you’re making the boba with molasses), sprinkle a pinch of tapioca starch over the dough and work it into the dough. Add more starch if the dough is still feeling very sticky.