Pour ¼ C milk into a small bowl, sprinkle the gelatin on top and give it a stir. Set aside.
In a mixing bowl, whisk together the egg yolks, sugar, and vanilla.
Heat ¾ C milk in a small saucepan. Bring the milk to a simmer over low heat.
Gradually pour the warmed milk into the egg yolk mixture while whisking the mixture. When all the milk has been poured into the egg mixture, pour it back into the saucepan and whisk over low heat for about 2 minutes.
Pour the milk with the gelatin into the saucepan, whisking over heat to dissolve the gelatin.
Transfer to a clean container to chill and set, which will take 2-4 hours.
Cut into cubes.
Assemble the bubble tea:
Place 2 tablespoon of regular homemade tapioca pearls at the bottom of a drinking glass.
Add 2 tablespoon of the small tapioca pearls.
Add in a few ice cubes.
Pour the milk tea over top of the ice cubes.
Layer the cut-up grass jelly and egg custard pudding.