Rinse the sushi rice under cold water until the water runs clear. In a saucepan, combine rinsed rice and 2.5 cups of water. Bring to a boil, reduce heat to low, cover, and simmer for 15-20 minutes until water is absorbed. Let stand covered for 10 minutes.

While rice stands, whisk together 1/4 cup rice vinegar, sugar, and salt for the rice seasoning. Gently fold this mixture into the cooked rice in a non-metallic bowl. Let it cool to room temperature.

Using a very sharp knife, cut the chilled, sushi-grade salmon into uniform 1/2-inch to 3/4-inch cubes. Place in a medium bowl and return to the refrigerator.

In a separate bowl, whisk together the low-sodium soy sauce, toasted sesame oil, 1 tablespoon of rice vinegar, and grated ginger to create the marinade.

Pour the marinade over the chilled salmon cubes. Add the 1/4 cup of sliced scallions and toasted sesame seeds. Gently fold to combine.

Divide the cooled sushi rice among four bowls. Arrange the marinated salmon on one side of the rice.

Add the toppings: diced avocado, sliced cucumber, and edamame. Garnish with extra scallions, nori strips, and a side of pickled ginger. Drizzle with spicy mayo if desired and serve immediately.