Rinse the sushi rice under cold water until it runs clear. This removes extra starch and prevents the rice from becoming gummy. I like to rinse mine at least three times for perfect texture.
Combine rinsed rice with water in a saucepan and bring to a boil. Reduce heat, cover, and cook until tender and water is absorbed, about 20 minutes. Stir in mirin and let the rice cool slightly.
Line a loaf pan with plastic wrap and press the cooked rice evenly inside. Make sure it’s tightly packed to create compact squares that hold together while frying. Chill in the fridge for at least one hour.
Lift the rice block from the pan and cut it into 8 even squares using a sharp knife. I like to wipe the knife between cuts to maintain clean edges.
Heat vegetable oil in a skillet to 375°F (190°C). Fry a few rice squares at a time until golden brown and crispy, about 2–3 minutes per side. Remove and drain on paper towels.
In a bowl, mix chopped shrimp, kewpie mayonnaise, sriracha, panko, green onions, and jalapeño. Stir gently to combine without breaking up the shrimp pieces.
Top each crispy rice square with a generous spoonful of the shrimp salad. Drizzle with eel sauce if desired and garnish with a small jalapeño slice or extra green onion.