01 - Combine rinsed sushi rice and water in a saucepan. Bring to a boil, cover tightly, reduce heat to low, and simmer for 15 minutes. Remove from heat and let stand covered for 10 minutes to complete steaming.
02 - Whisk together rice vinegar, sugar, and salt in a small bowl until completely dissolved. Gently fold the vinegar mixture into the warm rice using a cutting motion. Spread rice in a shallow layer to cool to room temperature.
03 - Moisten hands with water to prevent sticking. Form cooled rice into 12 compact rectangular or oval patties, approximately 2 inches long and 3/4 inch thick. Arrange on a parchment-lined baking sheet.
04 - Refrigerate rice pieces for 20 minutes to firm texture, ensuring they hold shape during frying.
05 - Combine diced salmon, mayonnaise, sriracha, soy sauce, green onion, sesame oil, and salt in a medium bowl. Mix gently until well incorporated. Refrigerate until assembly.
06 - Heat oil in a large nonstick skillet over medium-high heat. Fry rice pieces in batches, cooking 2 to 3 minutes per side until golden brown and crispy throughout. Transfer to paper towels to drain excess oil.
07 - Top each crispy rice cake with a slice of avocado. Spoon spicy salmon mixture generously over avocado. Garnish with toasted sesame seeds and microgreens or chives.
08 - Arrange on serving platter immediately. Serve with small bowl of soy sauce for dipping alongside the crispy rice pieces.