Place the water in a large skillet or pan over high heat. When the water is shivering, add the green beans and blanch for 10 minutes.

Remove the green beans and immediately plunge the beans into the ice water. Leave in the ice water for ten minutes, then remove and drain on a paper towel on a plate. Set aside.

Put the 1/2 cup water in a glass measuring cup and place in the microwave on high for 60 seconds or until hot. Add the miso and stir to dissolve the miso well.

Place the miso/water mixture back in the microwave on high for 20 seconds, then add the butter and stir until the butter melts.

Place the sesame oil in a skillet over medium-high heat, and when the oil is hot, add the garlic and sauté for 1 minute. Then add the white part of the green onion and the green beans and cook for 5 minutes, tossing frequently.

Add the white wine (or sake), stir, and cook for 2 minutes. Increase the heat to high and add the miso/butter mixture, the green tops of the green onion, the vinegar, and stir.

Cook for 2 minutes to allow the sauce to thicken, then sprinkle with the sesame seeds and serve.