Make the sauce
- Boil the soy sauce, sake, sugar and ginger for five minutes.
- Stir in the dashi and turn off the heat. Set aside.
Prepare the tofu
- Place the tofu between two stacks of kitchen paper and press lightly. Invert, press lightly again. Change the kitchen paper two more times, repeating the process.
- Cut the tofu into two-inch squares (or cubes).
- Place the starch in a shallow bowl. Add the tofu and gently roll each to completely coat the outside. Depending on how wet the tofu still is at this point, you may have to do the rolling part two to three times more.
Fry the tofu
- Pour enough cooking oil in a pan to reach a depth of at least three inches. Heat until wisps of smoke float on the surface.
- Fry the tofu, in batches of five or six, just until the coating turns crisp, about two minutes per batch. Drain on a stack of kitchen paper.
Serve the agedashi tofu
- Transfer the cooked tofu cubes on a shallow bowl. Spoon the dashi around them (you can keep in the excess in the fridge). Sprinkle the agedashi tofu with sliced scallions and serve at once.