In soup pot over medium heat, saute onion and ginger in olive oil until soft (3 min). Add celery, sweet potato, beans and mirin, and stir. Add kale and enough vegetable stock to cover all ingredients by an inch. Bring to a boil, reduce heat, cover and simmer for 30 minutes to cook potatoes through and allow flavors to develop. Season to taste with nutmeg, salt and pepper; and serve topped with gomashio or toasted sesame seeds.