Place mirin in a saucepan and heat over a medium heat for about 2 minutes to evapourate off the alcohol.
Add the dashi and soy sauce, simmer over a low heat for 3 minutes without a lid, then remove from the heat. Let it cool.
Cut the tofu in half lengthways, wrap each piece in a double layer of kitchen paper, and leave for about 10 minutes to absorb the liquid.
Cut each block of tofu into four equal pieces.
Coat all sides of the tofu evenly with cornflour.
Heat the olive oil in a frying pan over a medium heat, then place in the tofu. Cook for 1 minute, then reduce to a low–medium heat. Once the underside begins to firm up, turn the pieces over. Continue cooking, turning the tofu occasionally for 6–7 minutes until all sides are lightly golden.
Put the tofu on a plate lined with kitchen paper to absorb the oil.
Serve hot on a plate, pouring the mentsuyu with the salad onions to taste.
Notes
💡 Note: Mentsuyu - keep refrigerated, use within 1 week.