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 finish steaming.
02 - Whisk together rice vinegar, sugar, and salt in a small bowl until completely dissolved. Gently fold the seasoning mixture into the warm rice using a slicing motion. Spread the rice in a shallow layer and 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 pieces on a parchment-lined baking sheet.
04 - Refrigerate the shaped rice for 20 minutes until firm and cold. Chilling helps the patties hold their shape during frying and achieves better crispiness.
05 - Combine diced salmon, mayonnaise, sriracha, soy sauce, green onion, sesame oil, and salt in a mixing bowl. Fold gently to incorporate evenly without mashing the fish. 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 patty with a thin avocado slice followed by a generous spoonful of spicy salmon mixture. Sprinkle with toasted sesame seeds and finish with microgreens or chives.
08 - Arrange appetizers on a serving platter and serve immediately while rice remains crispy. Accompany with small bowls of soy sauce for dipping.