WARM THE MIRIN and sake in a saucepan over moderate heat. Remove the pan from the burner. Carefully, ignite the mixture and shake back and forth until the flame dies. Return pan to the burner and add the soy sauce, dashi and sugar; bring to a boil. Cool to room temperature. Set aside in a saucepan 1/2 cup of the teriyaki sauce. Dip pieces of meat (chicken, sliced beef, etc.) into remaining sauce to marinate. Grill meats. Reduce the sauce in the saucepan over high heat into a thickened glaze.