Boil a large pot of salted water.
Add 1 pound of fresh, trimmed green beans and cook for 3-4 minutes.
Drain the green beans in a colander, then immediately rinse them under cold water.
Whisk together 2 tablespoons of white miso paste, 1 tablespoon of soy sauce, 1 teaspoon of sesame oil, 1 tablespoon of rice vinegar, 1 teaspoon of sugar (if using), and 1 tablespoon of water in a mixing bowl until smooth.
Toss the blanched green beans in a large bowl with the prepared miso sauce until they are evenly coated.
Garnish your dish with 1 tablespoon of toasted sesame seeds and sliced scallions before serving.