Sauté the green beans in the oil over medium/medium-high until charred on at least one side, tossing occasionally, ~10 minutes
When cooked, add the scallion whites and garlic. Cook for 5 more minutes, tossing to make sure the green beans are well coated and charred all over.
Add the soy sauce, mirin, sugar, scallions, and garlic. Cook ~1 minute.
The more charred the green beans are, the more delicious they will be.Cook in a cast iron pan for extra char!Keep a splash guard handy. The green beans will spatter when they hit the oil because of their water content.