Add 100g strawberry ice cream and 20g strawberry syrup to a nonstick pan. Turn on medium-low heat, stir until the ice cream is simmering.
Quickly add 3 tbsps of cornstarch to the mixture, stir until dissolved.
Stir the mixture with a spatula for about 5 minutes until the mixture has been thickened - when you tilt the pan, the mixture won't flow like a liquid.
Turn off the heat, add 3 tbsps of cornstarch to the pan, mix with a spatula.
Transfer the dough out to a kneading bowl or a kneading mat.
Knead the dough with your hands until smooth. (If the dough is sticky, you can gradually mix in an extra 1 tsp of cornstarch to the dough. If the dough is too dry, you can add 1 tsp of strawberry syrup or water to the dough.)
Pinch small pieces of dough by hand, roll them into ¼-inch-diameter balls. (The boba dough will become dryer once it cools down. If the boba cracks when you roll it, you can add a little bit of water to the rest of the dough, knead the dough until it's smooth again.)
In a large pot, boil ⅔ pot of water. Use medium high heat. Add the bobas to the boiling water. Stir gently to prevent them from sticking to each other.
Once all the bobas are floating, cover the pot, simmer the bobas over low heat for 30 minutes.
Drain the bobas. Make them go through iced water for a chewier texture.