In a medium saucepan, bring water to a boil. Turn the heat down to medium. Add tapioca pearls, cook for 10 minutes, stirring often. Cover with a lid, remove from heat and set aside for 15 minutes. Most of the pearls should be completely transparent. It’s ok if a few have tiny white spots in the middle. Drain the tapioca pearls into a fine-mesh sieve and rinse under cold water until cool, stirring occasionally. Set aside to drain.
Meanwhile, preheat the oven to 400˚F. In a kettle over high heat, boil a few cups water.
When the pearls are ready, let’s make the custard. In a medium mixing bowl, add custard powder. Slowly whisk in half of the milk. Whisk in the eggs until combined.
In a medium saucepan over medium heat, combine the rest of the milk, evaporate milk, sugar and butter. Bring mixture just to a simmer, about 3 minutes, stirring often until sugar has dissolved. While whisking, slowly add in the custard. Cook until thickened, about 5 minutes. Remove from heat, mix in the tapioca pearls. The mixture would thicken more as it cools.
Prepare 6 (1-cup) ramekins. Fill each ramekin halfway full with tapioca mixture. Add 20 grams (1 tablespoon) lotus paste into each ramekin. Divide the rest of tapioca mixture into the ramekins. Slightly smooth the top.
Place the ramekins in a 9x13 baking pan. Slowly add hot water to baking pan until the water come about halfway up sides of ramekins. Carefully transfer to oven and bake for 20 minutes. Then, broil under broiler until the top is puffed with caramelized brown spots, about 3 – 5 minutes (If no broiler, turn the oven heat to 525˚F, and bake for about 5 minsutes). Remove from oven and remove from baking pan.
Set aside to cool for at least 15 minutes before serving. Serve hot, warm or at room temperature.