Make dashi stock. In a small saucepan, mix together the dashi powder and water over medium heat.
Add remaining ingredients. Once the dashi stock reaches a simmer, add the soy sauce, mirin, and sugar. Simmer for 3 minutes to burn off the alcohol in the mirin.
Serve. Remove from the heat and serve with your favorite tempura.
Notes
Quality ingredients: Since this tentsuyu sauce only has 5 ingredients, using high-quality authentic Japanese ingredients will ensure that you’ll have the best flavor.
Adjust to taste: Every person will have a different preference. For the perfect tempura sauce, adjust the soy sauce, mirin, and sugar to your liking.
Simmer the mirin. Since mirin has alcohol in it, simmering the sauce when you add the mirin will allow the alcohol to burn off leaving the rich sweet flavors behind.
Allow the tempura sauce to cool. Tentsuyu is typically served at room temperature. After making the sauce, allow it to cool before serving so the flavors have time to meld together.
Storage Instructions: You can store this tempura sauce in an airtight container in the refrigerator for up to 2 weeks.