Set up a steamer over high heat. Arrange the taro cubes in a single layer in the steamer basket.

Steam for 25 to 30 minutes until a skewer passes through each cube with no resistance.

Transfer the hot taro to a bowl and mash until smooth with a potato masher or fork.

Press the mashed taro through a fine-mesh sieve into a clean bowl to remove any fibrous strands. Set aside.

In a small bowl, whisk together the tapioca starch with 3 tablespoons of the measured coconut milk until fully dissolved. Set the slurry aside.

Pour the remaining coconut milk and the water into a medium heavy-bottomed saucepan. Add the pandan leaves if using.

Heat over medium heat, stirring occasionally, until the mixture is just steaming - about 3 minutes. Do not boil.

Remove the pandan leaves. Add the sugar and salt and stir until fully dissolved.

Add the sieved taro puree and whisk until completely smooth and incorporated.

Pour in the tapioca starch slurry while stirring constantly. Reduce heat to medium-low.

Stir continuously for 5 to 7 minutes until the mixture thickens noticeably and coats the back of a spoon in a thick, glossy layer.

Lightly oil a loaf tin or shallow square mold with a neutral oil. Pour the hot pudding mixture in and smooth the top with a spatula.

Let the pudding cool at room temperature for 20 minutes uncovered, then cover with plastic wrap pressed directly onto the surface.

Refrigerate for at least 4 hours, or overnight, until fully firm.

Run a thin knife around the edges, place a serving plate on top of the mold, and invert to release. Slice into portions and serve chilled.