1small headtatsoi, or pak choi, cut crosswise into 1-inch slices (about ½ lb)
1Tbsprice wine vinegar (not seasoned)
1Tbspgrated fresh ginger
¼tspSriracha sauce, or to taste
1-2Tbspwhite sesame seeds, toasted
Bring a large pot of salted water to a boil, and fill a large bowl with ice and water. Cut the tatsoi leaves in thick strips, and dump them all at once into the boiling water. Time – exactly 1 minute – then remove the leaves to the ice water to stop the cooking.
While the tatsoi cools, assemble the dressing – simply mix the soy sauce, sesame oil, rice wine vinegar, ginger, sugar, and Sriracha in a large bowl.
Drain the tatsoi leaves, squeeze them dry, and add them to the dressing. Toss vigorously to mix well. Chill at least 1/2 hour and up to 4 hours in the refrigerator.
At serving time, sprinkle with toasted sesame seeds.