Place beans into a large saucepan of boiling water; cook 5 minutes. Drain and plunge beans into ice water; drain.
Place ginger on several layers of damp cheesecloth. Gather edges of cheesecloth; squeeze cheesecloth bag over a small bowl. Set 1/2 teaspoon ginger juice aside; reserve remaining juice for another use. Discard ginger. Combine 1/2 teaspoon ginger juice, walnuts, water, miso, and soy sauce in a food processor; process until nuts are minced. Combine walnut mixture and beans in a large bowl.