Prepare a large steamer over medium heat, with enough water to steam for 45 minutes.
Peel the skin from both the orange and purple sweet potatoes. Remove both ends from each of the sweet potatoes. Cut them into small pieces, about 2-inch square in length. Give them a quick rinse to remove the debris.
Once the water is vigorously boiling, steam the sweet potatoes for 45 minutes, or until a fork can be poked through easily.
Meanwhile, mix together the tapioca flour, corn flour (cornstarch), granulated sugar, baking powder and salt in a large mixing bowl until well combined with a whisk. Set it aside.
Once the sweet potato pieces are done, remove them from the heat. Smash the orange sweet potato pieces through a fine mesh colander, or strainer, scraping the outer side often. When done, set aside. Wash the fine mesh thoroughly, and repeat for the purple sweet potatoes.
Add half of the flour mix to the smashed orange sweet potato, and mix thoroughly. Then, add 80ml of coconut cream to the mixture, and knead until it resembles a dough. Add 30ml of coconut cream, kneading until well combined. If it is too dry, add another 10ml of coconut cream. The dough should not be sticky or wet - it should resemble clay or play-doh. Set aside the amount that will be used, and wrap the rest in cling wrap tightly.
Repeat with the smashed purple sweet potato. Mix in the rest of the flour mix. Pour 100ml of coconut cream, kneading until combined. Add 25ml of coconut cream each time, until the dough is soft and resembles the consistency of play-doh. Set aside the amount that will be used, and wrap the rest in cling wrap tightly.
Roll the orange dough into long cylinders, before cutting them evenly, roughly about the same size as a ping pong ball. Roll each of the pieces into spherical shapes, and set them aside on a large plate. Repeat for the purple dough as well.
Over medium heat, pour 500ml of cooking oil, or sufficient to submerge the potato balls, into a wok. Let it heat up for about 3-4 minutes. Once the oil is warmed, add the orange balls one at a time, until 1/3 of the wok is filled. Let them cook for about 20 seconds.
Stir and turn the sweet potato balls for about 7-8 minutes over medium heat, continuously using a large strainer to gently press down and swirl the balls while frying. After 8 minutes, or until golden brown, remove them with the strainer, shaking off any excess oil and let them rest in a cooling rack. Repeat with the 2nd and 3rd batches of sweet potato balls, cooking each of them for 8 minutes.
Serve immediately.