1 cup (packed) light brown sugar
1 cup mirin
1 cup reduced-sodium soy sauce
1/2 cup Sake (optional)
2 tsp fresh grated ginger
Bring all ingredients to a boil in a small saucepan over medium heat, stirring to dissolve sugar. Reduce heat and gently simmer, stirring occasionally, until slightly thickened, 40–50 minutes; let cool. Teriyaki sauce can be made 1 month ahead. Store airtight and chill.