In a small mixing bowl, combine rice vinegar with sugar and salt then stir until dissolved. Pour the rice vinegar over cooked sushi rice and mix until well combined.
Transfer the rice to a baking pan lined with a plastic wrap. Gently press the rice to even it out. Cover and let it chill in the fridge for at least 4 hours or overnight.
Spicy Salmon
Chop the sushi-grade salmon into a small pieces, transfer it a a bowl then combine the salmon with mayo, sriracha, soy sauce, scallion and sesame oil. Mix well and set aside in the fridge until ready to use.
Once the rice chilled, cut into 16 rectangles. Heat vegetable oil in a pan over medium heat, fry the rice until both sides turns nice and golden. Remove from the heat and let it cool on a paper towel.
Top the crispy rice with a sliced avocado, a tablespoon of salmon mixture and sliced of jalapeno. Sprinkle it with black and white sesame seeds. Serve immediately.