Combine all ingredients in a small saucepan, bring to a boil, reduce heat and simmer for about 4 minutes. Remove from heat and let cool.
Store in the fridge for up to a week. Makes about 1 1/4 cups teriyaki sauce.
Mirinis a sweet Japanese rice wine, similar to sake but with a lower alcohol content and higher sugar content. If you don't have mirin, you can use sherry with a pinch of sugar added to it.NOTE: If using as a marinade omit the cornstarch and let the sauce cool completely before using.