For the soy-ginger sauce:
1/2 cup soy sauce
1/4 cup mirin
1/4 cup rice vinegar
2 green onions, including 2 inches of tender green tops, finely chopped
4 tsp. peeled and minced fresh ginger
For the filling:
1/2 lb.boneless pork loin, ground
1 1/2 oz. pork fatback, minced
2 oz. fresh shiitake or oyster mushrooms, brushed clean and tough stems removed, minced
2 Tbs. minced bamboo shoot
1 Tbs. peeled and finely grated fresh ginger
1 1/2 Tbs. cornstarch
1 Tbs. dry sherry
2 tsp. Asian sesame oil
1 tsp. sugar
3/4 tsp. fine sea salt
1/4 tsp. freshly ground pepper, to taste
30 round dumpling wrappers
To make the soy-ginger sauce, in a small bowl, whisk together the soy sauce, mirin, vinegar, green onions and ginger. Set aside until ready to serve.
To make the filling, in a bowl, combine the pork, fatback, mushrooms, bamboo shoot and ginger and stir briefly to combine. Add the cornstarch, sherry, sesame oil, sugar, salt and pepper and stir until the mixture has a smooth, even consistency.
Working with 1 dumpling wrapper at a time and keeping the others covered with a damp kitchen towel, assemble the shumai: Place a heaping 1 Tbs. of filling in the center of the wrapper. Cup it in your hand and, with the index finger and thumb of your other hand, pleat the top edge. Squeeze the dumpling gently in the center to indent slightly and tap the bottom to flatten. Using the back of a teaspoon dipped in water, pack the filling gently and smooth the top. Repeat with the remaining filling and wrappers to make 24 dumplings. (The extra dumpling wrappers allow you to lose a few while practicing.)
In a wok or large, wide saucepan, pour in water to a depth of 2 inches and bring to a boil over high heat.I have the most awesome cast iron wok! Place the basket in the wok Transfer the dumplings to a large, wide, shallow platter and keep warm in a 200°F oven while you steam the remaining dumplings.
Serve the dumplings immediately. Pass the soy-ginger sauce at the table or serve it in individual dipping bowls. Serves 4 to 6.