In the West, custards are almost always made
with milk or cream, but just about any liquid
will do as long as it contains some dissolved
minerals. Mix an egg with a cup of plain
water and you get curdled egg floating in
water; include a pinch of salt and you get a
coherent gel. Without minerals, the negatively
charged, mutually repelling protein molecules
avoid each other as they unfold in the heat,
and each forms only a few bonds with a few
others. With minerals, positively charged ions
cluster around the negatively charged proteins
and provide a neutralizing shield, which
makes it possible for the proteins to unfold
near each other and bond extensively into a
fine network. Meats are rich in minerals, and
the Japanese make savory custards, chawan-
mushi (soft) and tamago dofu (firm), from
both bonito and chicken broths. Vegetable
stocks also work.
Proportions The consistency of a custard can