Make the base: In a bowl, combine rice flour, palm sugar, tapioca starch, arrowroot flour, thick coconut milk, and thin coconut milk. Use your hands to mix until the sugar is completely dissolved. Strain the mixture through a fine mesh sieve and set aside.

Make the topping: In another bowl, mix rice flour, water, salt, and thick coconut milk. Use your hands to mix until smooth and no lumps remain. Strain through a fine mesh sieve and set aside.

Steam the small cups for about 10 minutes to prevent sticking.

Pour the base mixture into the cups, filling them just over halfway. Cover and steam for 10-15 minutes. When done, remove from heat and let rest for 1-2 minutes.

Pour the coconut topping mixture over the base to fill the cups. Steam for another 5-10 minutes until set. Remove from heat and let cool for about 10 minutes.

Gently use a spatula or a wet popsicle stick to remove the cakes from the cups. Arrange on a plate and serve.