Step 1: Rinse 1.5 cups of sushi rice under cold water until the water runs clear. This usually takes about 5-7 rinses.
Step 2: Cook the rice according to package directions. For most sushi rice, this means combining 1.5 cups rice with 1.75 cups water in a pot, bringing to a boil, then reducing heat to low, covering, and simmering for 15 minutes. Remove from heat and let it steam, covered, for another 10 minutes. Do not lift the lid!
Step 3: While the rice cooks, prepare the sushi vinegar mixture. In a small saucepan, combine 2 tablespoons rice vinegar, 1 tablespoon sugar, and 1/2 teaspoon salt. Heat gently until sugar and salt dissolve. Let cool slightly.
Step 4: Transfer the cooked rice to a large, wide bowl. Pour the sushi vinegar mixture evenly over the rice. Using a cutting motion with a rice paddle or wooden spoon, gently fold the seasoning into the rice. Avoid mashing. Fan the rice (with a small fan or piece of cardboard) as you mix to cool it quickly and give it a glossy finish. Let cool completely.
Step 5: Once the rice is cool, press it firmly into a shallow, rectangular pan (about 8x8 inches) lined with plastic wrap. Aim for a thickness of about 1/2 to 3/4 inch. Press down very firmly to ensure the blocks hold together. Chill in the refrigerator for at least 30 minutes, or up to several hours.
Step 6: Once chilled, carefully lift the rice block out using the plastic wrap. Remove the plastic wrap and cut the rice into 12-16 rectangular pieces (about 1.5x2 inches). Pro Tip: Use a sharp knife dipped in water to get clean cuts.
Step 7: Heat about 1/2 inch of neutral oil (like canola or vegetable oil) in a large non-stick skillet over medium-high heat. Once shimmering, carefully place the rice blocks into the hot oil, ensuring not to overcrowd the pan. Fry for 3-4 minutes per side, or until deeply golden brown and crispy. Transfer the crispy rice to a wire rack lined with paper towels to drain excess oil. Season lightly with a pinch of sea salt.
Step 8: Finely dice 8 oz of sushi-grade tuna. Aim for small, uniform pieces.
Step 9: In a medium bowl, combine the diced tuna with 1/4 cup Japanese mayonnaise (Kewpie), 1-2 tablespoons sriracha (to taste), 1 teaspoon sesame oil, 1 teaspoon soy sauce, and 1/2 teaspoon chili garlic sauce (optional, for extra kick). Gently mix until the tuna is well coated. Taste and adjust seasoning as needed.
Step 10: Assemble the Nobu Style Spicy Tuna Crispy Rice. Top each crispy rice block with a generous spoonful of the spicy tuna mixture. Garnish with thinly sliced jalapeño, a sprinkle of chives or scallions, and a few black sesame seeds if desired. Serve immediately.