Blanch the green beans: Bring a pot of water to a rolling boil. Add the trimmed green beans and blanch for about 3 minutes until they attain a bright green color and a tender-crisp texture. Drain and set aside.
Mix the sauce: Add the soy sauce, hoisin sauce, brown sugar, and rice vinegar to the skillet. Stir to combine, letting flavors meld together.
Combine the green beans: Add the drained green beans to the skillet. Toss in the sauce, ensuring every bean is coated. Continue cooking for 2-3 minutes until heated through.
Garnish and serve: Remove from heat and garnish with sesame seeds. Serve immediately.
Notes
For a crunchy texture, consider adding toasted walnuts or slivered almonds. Adjust the sauce ingredients to your taste.