In a large mixing bowl, combine the glutinous rice flour, tapioca starch, coconut milk, baking powder, and salt. If desired, mix in the shredded coconut. Knead the mixture until it forms a smooth dough.
Shape the dough into smooth balls, about one inch (2.5 cm.) in diameter.
Prick the balls with a toothpick or metal pin which has been dipped in rice flour to help prevent the karioka from bursting while they cook.
Heat oil in a Dutch oven or pot over medium-high heat until it reaches 350°F (175°C). Use a frying thermometer, or make in a tabletop deep fryer or an air-fryer.
Carefully add the dough balls to the hot oil, frying in batches to avoid overcrowding the pan. Fry until the karioka balls are golden brown and crispy, approximately 4-6 minutes. Use a slotted spoon to transfer the cooked balls to a wire rack suspended over a baking pan to let the balls drain and cool.
In a small saucepan, combine the palm sugar, coconut milk, ube extract, and vanilla powder. Cook over medium heat, stirring constantly, until the sugar is fully dissolved and the mixture thickens slightly, around 5 minutes. Remove from heat.
Skewer the fried balls onto a Woden skewer or reusable metal skewer. A typical serving is to place 3 balls on each skewer, but I 100% trust you to control the portion size as you like.
Allow the glaze to cool slightly before dipping the skewered karioka balls. Ensure each ball is evenly coated on all sides with the glaze. Return the dipped skewers to the wire rack to set for a few minutes.
Serve the karioka warm, optionally garnished with additional shredded coconut.