Mix all ingredients except the horseradish, ginger and lemon juice. Bring to a boil, and remove from heat. Grate the radish.
For serving, put warm sauce into individual bowls. Place a heap of the radish topped with horseradish on each plate of fried food.
Each person should mix as much of this with his sauce as suits his taste. Add the lemon juice if desired. This sauce used mainly with Tempura.