This soup tastes best made ahead then slowly reheated before serving.
In Dutch oven or soup pot over medium to medium low heat, sauté onion and cabbage in butter for 5 minutes or until soft.
Add tomato, potato, celery, celery leaves and garlic, stir and cook 8 minutes until tomato can be easily broken down with a wooden spoon. Add beans, broth, water, dill and bay leaf and bring to a boil.
Cover, reduce heat. Simmer 45 minutes until all vegetables are tender.
Blend flour with sour cream, add a few spoonfuls of soup stock, stir and slowly add mixture back to soup, stirring constantly. Bring back to a gentle simmer and cook 2-3 minutes. Add mustard and stir. Season with salt and pepper to taste. Garnish with fresh chopped dill before serving.
Serving Size 1 cup
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.