Rinse the sushi rice under cold water until the water runs clear., Combine the rinsed rice and water in a rice cooker or pot and cook according to the appliance’s instructions. Let the rice cool slightly once done., In a small bowl, mix rice vinegar, sugar, and salt until dissolved. Pour this mixture over the rice while it’s still warm, mixing gently with a wooden spatula to coat., Slice the salmon fillet into small pieces or cubes, depending on your preference. Marinate it in soy sauce and mirin for about 20 minutes., Lightly oil a frying pan over medium heat. Spread a layer of seasoned sushi rice in the pan and press down firmly. Cook for about 5-7 minutes or until the bottom is crispy and golden., In a clean skillet, add a touch of sesame oil over medium-high heat. Once hot, add the marinated salmon and cook for a few minutes on each side until it’s fully cooked and flakes easily., Once the rice is crispy, add the cooked salmon on top. If using avocado, lay slices over the salmon, adding a creamy texture to the dish., Sprinkle sesame seeds, chopped coriander, and green onions over the top as a finishing touch to enhance flavors.