Rinse 1 cup of sushi rice under cold water until the water runs clear. Combine with 1 ¼ cups of water and a pinch of salt in a saucepan. Bring to boil, reduce to low and cover. Simmer for 15 minutes. Fluff the rice with a fork, stir in 2 tablespoons of rice vinegar, and let sit covered for 10 minutes.

Heat 1 tablespoon of olive oil in a skillet over medium heat. Cook 1 pound of large shrimp for 2-3 minutes on each side until opaque and pink. Mix 2 tablespoons of soy sauce, 1 teaspoon of rice vinegar, 1 teaspoon of sesame oil, and ½ teaspoon of sugar in a bowl. Drizzle this over shrimp and cook for 1 additional minute.

Prepare spicy mayo by combining ¼ cup of mayonnaise and 1 tablespoon of sriracha in a small bowl. Stir until smooth. Adjust spice to taste.

Assemble stacks using a round mold or glass. Start with a base layer of sushi rice, add layer of cooked shrimp, then slices of avocado and cucumber. Press each layer slightly to ensure stability.

Remove the mold or glass, drizzle with spicy mayo, sprinkle sesame seeds, and garnish with fresh cilantro or green onions. Serve immediately.