In a large saucepan, add salted boiling water and rice, and boil for 10 minutes
Drain the cooked rice using a colander and rinseit
Set the colander over a kettle of boiling water,ensuring that the rice does not touch the water. Cover it with a kitchen toweland lid. Steam the rice for 10-15 minutes until it becomes fluffy and dry.Check the water level in the kettle occasionally and add water if needed.
While the rice is steaming, take a small saucepan and bring 1/4 cup of vinegar to boil with sugar and salt. Stir until the sugar dissolves and then remove the saucepan from the heat.
In a small skillet, dry-roast the sesame seeds over moderate heat until golden and fragrant. Transfer them to a small bowl.
Once the rice is done, transfer it to a large bowl and stir in the vinegar mixture. Let the rice cool, and then stir in the sesame seeds, remaining 3 tablespoons of vinegar, oil, ginger, scallions, carrot, and cucumber. The salad can be made up to this point 1 day ahead and chilled, covered. Bring it to room temperature before proceeding
Dry-roast the nori sheets, one at a time,directly over moderate heat (gas or electric burner) until they turn brightg reen for 30 seconds to 1 minute. Cut the nori sheets into thin, 2-inch-longstrips using scissors.
Peel and pit the avocado, and then quarter it. Cut it crosswise into thin slices. Add the avocado to the salad along with surimi(if using) and two-thirds of the nori strips. Toss well.
Make the dressing by stirring the wasabi powder into hot water in a small bowl. Then stir in cold water, soy sauce, and ginger juice
Serve the salad sprinkled with the remaining nori strips and drizzled with the dressing.