1 cupsugarwhite or brown sugar, or a combo of both
Combine the soy sauce, mirin, and sugar in large, deep stockpot or pan. Bring to a soft boil over medium-high heat. Once bubbling, lower the heat and simmer (no lid). Stir frequently. The sauce will gradually thicken as it reduces. At about the 30-minute mark, if you wanted to add additional ingredients, now is the time. Reduce the sauce until it reaches the consistency you like, however, it will continue to thicken as cooled and then chilled. I shoot for coating the back of a spoon and I look for a glossy, silky consistency. Cool completely before jarring up, then refrigerate.