Bring 1 liter water to a boil in a 3-quart / 2.8 L saucepan with the 3 knotted pandan leaves.

Add the orange sweet potato, purple sweet potato, and taro. Simmer for 6 to 8 minutes until a fork slides through easily but the cubes still hold their shape. Drain and set aside, discard the pandan leaves. Do not undercook the taro, raw taro can irritate the throat.

Bring 800 ml water to a boil in a 2-quart / 1.9 L saucepan. Add the sago pearls and stir once so they don't stick to the bottom.

Simmer for 12 to 15 minutes, stirring occasionally, until the pearls turn fully translucent with no white core left.

Drain the sago in a fine-mesh sieve and rinse under cool running water for 30 seconds to keep the pearls loose.

Combine the coconut milk, remaining pandan leaf, palm sugar, granulated sugar, and salt in the rinsed-out 3-quart / 2.8 L saucepan. Warm over medium-low heat, stirring, until the sugar dissolves, about 3 minutes.

Add the sweet corn kernels if using and simmer gently for 2 minutes. Keep the heat low, a hard boil can split the coconut milk.

Stir the cooked root vegetables and drained sago into the coconut broth. Simmer for 2 to 3 minutes, just until everything is warmed through.

Taste and adjust sweetness, cold portions need more sugar than warm ones. Discard the pandan leaf before serving.

Ladle into bowls and serve warm, or chill for at least 2 hours and serve cold over ice.