Mix rice vinegar, sugar, and salt until dissolved. Pour the seasoning into the cooked rice and fold to combine. Let rest for 10-15 minutes to absorb.
Place seasoned rice in a 5” by 9” pan and cover loosely with plastic wrap. Press down with a spatula to create a dense, evenly flat block without air pockets.
Cover and refrigerate for at least 8 hours or 1 hour in the freezer.
Cut the rice block into 16 rectangles. Put the rice rectangles into the freezer.
Mince the salmon, place in a bowl, add mayo and sriracha, and combine.
Place cornstarch in a pan and coat each rice rectangle evenly.
Deep-fry in oil at 375°F for 2-3 minutes until crisp. Transfer to wire rack to cool.
Slice jalapeño and avocado into thin slices. Mash avocado with lime juice.
Place ½ tablespoon of avocado, followed by 1 tablespoon of spicy salmon on each rice cake, and top with a slice of jalapeño. Enjoy!