Prepare the batter: In a bowl, combine 1 cup of flour and 1/2 cup of cornstarch. Gradually add 1 cup of ice-cold water, mixing gently until the batter is smooth.

Season the chicken: Cut chicken breasts into thin strips and season with salt and pepper.

Dip and fry: Heat oil in a pan to 350°F (175°C). Dip the chicken strips into the batter, ensuring they are fully coated. Cook the chicken strips in small batches, frying them until they turn golden brown and develop a crispy texture.

Drain: Remove the chicken from the oil and place it on paper towels to drain excess oil.

Rinse the rice: Measure out 2 cups of sushi rice and rinse under cold water until the water runs clear.

Cook the rice: Follow the cooking instructions on the rice package to prepare it.

Season the rice: While the rice is still warm, mix in 1/4 cup of rice vinegar, 2 tablespoons of sugar, and 1 teaspoon of salt. Stir well to combine and let it cool to room temperature.

Prepare your workspace: Place a bamboo sushi mat on a clean, flat surface, then position a sheet of nori on the mat with the shiny side facing down.

Add the rice: Wet your fingers to prevent sticking, then spread a thin layer of seasoned sushi rice over the nori, leaving about 1 inch of space at the top edge.

Add the fillings: Place a few pieces of tempura chicken, cucumber strips, and avocado slices across the center of the rice.

Start rolling: Lift the edge of the bamboo mat closest to you and begin rolling the sushi tightly, using the mat to guide and shape the roll.

Seal the roll: Dampen the top edge of the nori with a small amount of water to ensure the roll seals securely.

Slice: Slice the roll into bite-sized pieces using a sharp knife for clean cuts. Clean the knife with a damp cloth between cuts to maintain smooth, clean slices.

Arrange the sushi pieces on a plate.

Serve with soy sauce on the side.

For an extra burst of flavor, drizzle with sweet chili sauce or eel sauce, if desired.