I adore matcha in my desserts. Sure there is the earthy, grassy flavor, but there is also the wonderful pale green color. This is essentially the recipe for a thick match tapioca pudding which happens to make a great filling for a cupcake. Note that it needs to be refrigerated for at least an hour before using as a filling.
Cover the tapioca pearls in warm water in a bowl and let sit on the counter for 20 minutes. Drain the pearls.
Heat milk, coconut milk, salt, and pearls over medium-high heat until boiling.
Reduce heat to low and continue cooking, stirring regularly, until tapioca balls are translucent and chewy, approximately 3-5 minutes.
While milk and tapioca are coming to a boil, whisk egg yolks in a small bowl and gradually add sugar. Add matcha and whisk together.
Add a small amount of the heated milk mixture to the egg mixture, whisking continuously.
Pour the egg mixture back into the milk mixture and continue to heat over medium-low heat, stirring constantly until slightly thickened about 5 minutes.
Transfer to a heatproof bowl. Let sit at room temperature until cool. Cover with plastic wrap and transfer to the refrigerator until cold, about 1 hour.
You can make this in advance and store it in the refrigerator overnight in a covered container.