1. Wash the rice in cold water until the water runs clear, then drain. Add the rice and water to a rice cooker or stovetop pot and cook according to the instructions.

2. Let the rice cool for a few minutes after cooking. In a small bowl, mix the rice vinegar, sugar, and salt until dissolved. Gently fold the mixture into the cooked rice. Set the rice aside and cover with a damp cloth to prevent drying out.

3. In a bowl, whisk the eggs together with sugar, mirin, soy sauce, salt, and dashi (if using) until well combined.

4. Heat a non-stick rectangular tamagoyaki pan (or a small non-stick round pan) over medium-low heat and lightly oil it. Pour a thin layer of the egg mixture into the pan and swirl to coat.

5. Once the egg is mostly cooked but still slightly soft on top, roll it into a log shape from one side to the other using a spatula or chopsticks. Push the rolled omelette to one side of the pan.

 6. Add another thin layer of the egg mixture to the pan, lifting the rolled egg so the new layer coats underneath it. Roll the omelette again and repeat until all the egg mixture is used. The omelette should form a neat rectangular or cylindrical shape.

7. Once done, transfer the omelette to a cutting board and allow it to cool slightly. Slice it into ½-inch thick pieces.

8. Shape the Sushi Rice: Wet your hands to prevent sticking, then take a small handful (about 1-2 tbsp) of sushi rice and gently form it into an oval or rectangular shape, creating a small rice ball (nigiri shape).

9. Place a slice of tamago omelette on top of the shaped rice ball. Wrap a thin strip of nori around the middle to hold the tamago and rice together. You can use a bit of water to seal the nori if needed.

10. Serve your tamago sushi with soy sauce, wasabi, and pickled ginger (gari) on the side. Enjoy as part of a sushi platter with other nigiri or sushi rolls.