Rinse the tofu slices in boiling water for a few seconds to remove excess oil. Drain and pat dry.
Heat the Basic Dashi Soup Stock, saké, soy sauce, sugar and mirin in a saucepan and bring to a boil. Reduce the heat, add the tofu and simmer for 10 minutes. Drain and allow the tofu to cool completely. Cut the tofu slices in half, either diagonally or cross