Heat 1 tablespoon of sesame oil in a large pot or Dutch oven over medium-high heat. Add 1 lb of thinly sliced beef (such as chuck or sirloin) and cook until browned on all sides. Remove the beef from the pot and set aside.

Add 1 medium yellow onion, sliced, and 2 cloves of minced garlic to the pot. Cook until softened, about 3 minutes. Add 1 lb of Yukon gold potatoes, peeled and cut into 2-inch chunks and 1 large carrot, peeled and cut into 1-inch pieces. Stir and cook for another 3 minutes.

Return the browned beef to the pot. Pour in 3 cups of dashi broth. Add 1/4 cup soy sauce, 2 tablespoons of mirin, 1 tablespoon sake, and 1 tablespoon of granulated sugar. Stir well.

Bring the mixture to a simmer, then reduce the heat to low, cover, and cook for 30-40 minutes, or until the potatoes and carrots are tender. Add 4 oz of green beans, trimmed and halved in the last 5 minutes.

Remove from heat and let the stew sit for 5 minutes. Garnish with chopped scallions.