Bring800ml (28fl oz) Basic Dashi Stock to the boil in a saucepan over medium heat. Add 1tablespoonsoy sauce, 2teaspoonssake, ¼teaspoonsea salt and 10g (¼oz) peeled and finely grated fresh ginger.
Combine3tablespoonswater with 3tablespoonscornflour (cornstarch) in a bowl. Take the pan off the heat and mix in the cornflour mixture.
Place the pan back on the heat and cook until the soup thickens. Pour in 2 lightly beaten eggs, slowly swirling around the pan. When the egg is partially set, serve in bowls with a sprinkle of thinly sliced spring onions (scallions).