In a medium bowl, mix ½ cup warm water (approximately 100°F), yeast, and 1 teaspoon sugar until combined. Let it rest for 10 min. or until it becomes frothy.
In a large mixing bowl, sift the rice flour, tapioca starch, and salt. Add two cups of warm water and whisk until smooth. Pour in the activated yeast mixture and whisk to combine. Cover the batter with a lid and let it rest for at least 2 hours.
After 2 hours, heat the coconut milk with the sugar in a saucepan on low heat, stirring until the sugar dissolves. Make sure the mixture is no hotter than 100°F.
Add the coconut milk with sugar, plus the vanilla extract to the yeast batter and stir. Pop any bubbles on top to avoid air bubbles in the finished cakes.
If using food coloring, divide the batter into 4 medium bowls. Add a few drops of coloring to three of the bowls and stir to combine. Let rest for 30 minutes.
Grease cake molds or a mini muffin pan. Fill the steamer basin ¾ full with water. Place the molds or pan into the steamer and bring the water to a boil.
Stir the batter and pour some until ¾ of each mold. Cover the steamer and let them steam for 6 minutes on medium heat or until a toothpick comes out clean.
Remove the molds from the steamer and allow to cool for 5 minutes.
Serve steamed rice cakes with optional coconut sauce (see above). Enjoy!