Cut away and discard any membranes or peripheral fat from the chicken breast.

Place the chicken breast on a flat surface and cut it into the thinnest possible slices.

Stack the slices and cut them into very thin shreds.

Cut the shreds into very fine cubes.

Chop the cubes with a cleaver or a heavy sharp knife.

Alternatively, blend the chicken in a food processor, but do not process to a paste.

Chop the shrimp by hand or in a food processor until it has the same consistency as the chicken.

Combine the chicken and shrimp in a mixing bowl and add the egg white.

Add the cornstarch, salt, sugar, and soy sauce and blend.

Blend the ginger and Shaoxing wine.

Squeeze to extract the liquid from the ginger mixture.

Discard the ginger solids.

Add the ginger-wine liquid to the chicken and shrimp mixture.

Beat the mixture briskly for about five minutes.

Add the green onion and coriander and blend well.

If the won-ton skins are square, cut them into rounds or circles.

To do this, stack the won-ton skins and cut them into circles about three inches in diameter.

Cut around with a cleaver, a sharp knife, or a three-inch biscuit cutter.

Hold one round won-ton skin in your hand and fill the center with one tablespoon of the chicken and shrimp filling.

Bring up the edges of the won-ton skin to enclose the filling all around, but leaving the top of the meat mixture exposed.

Smooth over the top.

As the shu mai are filled, arrange them open side up on a steamer rack without crowding.

Bring water to a boil in the bottom of a steamer.

Place the rack with shu mai over the boiling water and cover tightly.

Let steam for eight minutes, or until the filling is cooked through.

Serve immediately with optional dipping sauce (vinegar, soy sauce, Sichuan paste, and hot mustard).