Bring a large pot of lightly salted water to a boil.
Add the green beans and cook uncovered until tender, about 3 minutes.
Drain in a colander and immediately immerse in ice water for several minutes until cold to stop the cooking process. Once the green beans are cold, drain well and cut into 2-inch pieces.
While the green beans are cooking, stir together the peanut butter, sugar, soy sauce, peanuts, and miso paste in a mixing bowl. Once the green beans have been cut, stir into the peanut sauce and serve.
