Bring 3 cups dried shiitake mushrooms (about 3 ounces), 1/3 cup reduced-sodium soy sauce, 1 tablespoon raw or brown sugar, and 1 cup water to a boil in a small saucepan. Cover pan; reduce heat to medium-low. Simmer, stirring occasionally, until mushrooms are softened and all liquid is absorbed, 12-15 minutes.
Let mushrooms cool slightly, then thinly slice. Transfer to a small bowl, add 1/2 teaspoon toasted sesame seeds, and season with freshly ground black pepper.
