Rinse the sushi rice thoroughly in cold water. Place in a small saucepan and add the water and the salt. Cook the rice as per packet instructions, then remove from heat and leave to sit for 5 minutes.
In a small bowl, mix the rice vinegar & sugar together until the sugar has dissolved. When the rice is cooked, pour over the vinegar mixture and mix to coat.
Line a slice tin (27cm x 17cm) with cling film and add the rice into the tray. Use a lightly greased spatula or spoon to press the rice down into an even layer. Cover and allow the rice to cool before transferring to the fridge to set for at least 1 hour, or ideally overnight.
Once the rice is cooled, remove from the tray and cut into 12 squares.
At this stage, cook the Karaage chicken in the oven or air fryer as per packet instructions. When they have finished cooking, cut any larger pieces in half so that they are the same size as the rice squares.
While the chicken is cooking, heat the vegetable oil in a large fry pan over medium-high heat. Working in batches, shallow fry the rice squares for about 3 minutes each side, until crispy and golden. Place on a wire rack or on paper towels to soak up any excess oil.
Mix the sriracha and mayonnaise together to make your sauce.
Transfer the crispy rice cakes to a large serving platter. Top each with some slices of avocado & a piece of the Karaage chicken. Drizzle over the sriracha mayo and garnish with sesame seeds and sliced spring onions or chives.