How do I keep a custard from breaking? I have a recipe for a steamed egg and ginger pudding. It can be eaten hot or cold, and I prefer it cold. The problem is that it starts to separate in the fridge (liquid accumulating where I've scooped pudding out, or sometimes around the edge of the bowl). How do I prevent that?

I did look at this discussion, but I can't tell whether it's relevant.

Recipe, in case it's relevant

2 C water
4 oz. ginger root
4 oz. Chinese rock sugar
4 large eggs, beaten
2/3 C milk
a few drops vegetable oil

Set up a stovetop steamer.
Slice ginger.
Bring water to a boil; boil ginger 2 min. Discard ginger slices.
Dissolve rock sugar in boiling water.
Remove pot from heat.
Add milk to the pot; whisk in eggs and vegetable oil.
Pour into bowl or bowls and steam 12 min.
A weeping custard is practically always an overheated custard. First wait that your pot has cooled down sufficiently before adding the eggs (somewhere below 70 C is good), temper them instead of throwing them into the pot, and steam using a thermometer, not a clock. Try 85 C as the first goal and see if it works well or needs adjustment.