How to Make It
In a saucepan set over medium heat, combine the soy sauce, mirin, ½ cup water, sake, and bonito flakes. Bring to a full rolling boil; then remove the pan from the heat and let cool. Strain the cooled sauce, discarding the solids. The sauce will keep in an airtight container in the fridge forever.
Sweet Potatoes: Roasted, Loaded, Fried, and Made Into Pie