Rinse 1 cup of sushi rice under cold water until it runs clear. Combine with 1 ¼ cups of water in a medium saucepan, bring to a boil, reduce heat to low, cover, and simmer for 15 minutes. Remove from heat, add 2 tablespoons of rice vinegar and a pinch of salt, stir gently, and let it sit covered for 10 minutes.

Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Add 1 pound of large shrimp and cook for 2–3 minutes per side until pink and opaque. Mix 2 tablespoons each of soy sauce, rice vinegar, and sesame oil with 1 teaspoon of sugar and drizzle over shrimp. Stir for an additional minute until well coated.

In a small bowl, combine ¼ cup of mayonnaise with 1 tablespoon of sriracha, adjusting to desired heat level. Stir until smooth.

Layer sushi rice at the bottom of a round mold, press down. Add spicy shrimp, slices of avocado and cucumber. Repeat layering until all ingredients are used, finishing with rice on top.

Remove the stacks from the mold and place on a serving platter. Drizzle with spicy mayo and sprinkle with sesame seeds. Garnish with cilantro or green onions if desired. Serve immediately.