Line up the green beans, cut off the tough stem ends, and cut them into bite-size lengths, 2-3 pieces per bean.
Bring a small pot of water to a boil and add the salt (about 1 tsp per 500 ml of water). Boil the beans 2 minutes if thin, 3 minutes if thick, until cooked through but still with some bite.
Drain, cool the beans immediately in cold water to keep the color bright, then dry them thoroughly with a paper towel. Any water left on the beans will dilute the dressing.
Grind the sesame seeds until about half are crushed and half are still whole. Stir in the sugar and soy sauce to make a thick, sandy paste. Taste and adjust the sugar.
Add the dried beans and toss until evenly coated. Serve cold or at room temperature.
