Cook the Sushi Rice: First, rinse the sushi rice under cold water until the water runs clear. This removes excess starch and is a crucial step for the right texture. Cook the rice with the 650ml of water according to your package instructions or in a rice cooker.

Season the Rice: While the rice is cooking, prepare the seasoning. In a small bowl, whisk together the rice vinegar, caster sugar, and salt until dissolved. Once the rice is cooked, transfer it to a large, non-metallic bowl. Gently pour the vinegar mixture over the hot rice and use a rice paddle or spatula to fold it in, using a cutting motion to avoid mashing the grains. Let it cool slightly. For a fantastic guide on getting this right, Serious Eats has a detailed tutorial.

Prepare the Topping: In a separate mixing bowl, combine the softened cream cheese, Kewpie mayonnaise, sriracha, and soy sauce. Mix until smooth. Gently fold in the flaked crab meat, chopped prawns, and one finely sliced spring onion. Be careful not to overmix; you want to keep some texture in the seafood.

Assemble the Casserole: Preheat your oven to 180°C (160°C fan). Take a 9x13 inch (or similar size) baking dish and press the seasoned sushi rice evenly into the bottom, creating a compact layer. What works best for me is using the back of a wet spoon to prevent the rice from sticking.

Add the Creamy Layer: Spoon the creamy seafood mixture over the rice base and spread it out into an even layer, reaching all the way to the edges of the dish.

Bake to Perfection: Place the dish in the preheated oven and bake for 10-15 minutes, or until the topping is heated through and bubbling at the edges. For a more golden-brown top, you can switch the oven to the grill setting for the last 1-2 minutes, but watch it closely to prevent it from burning.

Garnish and Serve: Remove the casserole from the oven. Sprinkle generously with furikake, the remaining sliced spring onion, and toasted sesame seeds. Arrange the sliced avocado on top.

Enjoy: Serve the Creamy Sushi Bake Casserole warm, with the small nori sheets on the side for scooping. Each person can scoop a portion onto their nori sheet and eat it like a small hand-roll.