1/4 cup soy sauce
1/4 cup brown sugar
2 tablespoons mirin
1 tablespoon oyster sauce
1 tablespoon water
1 teaspoon sesame oil
1 clove garlic, minced
1 teaspoon cornstarch mixed with 1 tablespoon water, optional for thickening
Combine soy sauce, brown sugar, mirin, oyster sauce, water, sesame oil, and garlic in a small saucepan
Heat over medium, stirring until sugar dissolves
Simmer for 2 to 3 minutes
Add cornstarch slurry if a thicker sauce is desired
Stir until glossy and slightly thickened
Remove from heat and cool before using on Spam musubi