In a bowl, mix the eggs with the soy sauce, dashi and mirin. Next, empty half of the bowl’s contents into a non-stick pan. Cook the omelette at a low temperature, ensuring that it does not lose its moisture. Repeat the process with the other half of the bowl’s contents.
Once you have made two omelettes, cut them into a square shape to match the dimensions of the nori seaweed, leaving a 2cm long space at one end of the nori seaweed to make it easier to roll. Place one sheet of nori seaweed on a makisu (bamboo mat), with the shiniest part face down. Place one of the omelettes on top of this, then roll them together. Repeat the process with the second omelette.
Cut the roll three times to obtain 4 pieces of rolled tuna omelette and seaweed. Place a tuna chunk on top of each one. Serve with a little soy sauce in a small bowl.