I have unseasoned rice vinegar but a recipe that calls for seasoned. I assume I should add sugar and salt to substitute for seasoned vinegar, but in what proportions would mimic a typical seasoned rice vinegar?
For each cup of vinegar, add 3 tablespoons of sugar and one tablespoon of salt. You may also add a piece of kelp or a pinch of kelp powder. And of course, all of these proportions can be adjusted to taste.
From my favorite Japanese cooking site, JustHungry:
Mix 1/4 cup of rice vinegar or mild cider vinegar, 1 tablespoon of sugar, 1/2 tablespoon of mirin, sake or sweet brandy, and 1/2 tablespoon of salt. Heat over low heat in a small saucepan, and stir until the sugar and salt have dissolved. This is enough to flavor 4 cups of rice, so adjust the amount according to the amount of rice you have.