Bring the 3 types of cabbage to the boil in a pan of water and simmer for approx. 10 - 15 minutes.
Bring the soup vegetables to the boil in a separate pan.
Peel the sweet potatoes and cut into wedges.
Bake in a preheated oven at 170 degrees Celsius for approx. 25 minutes.
When the cauliflower, broccoli and romanesco are soft, strain the vegetable stock through a sieve.
Blend the cabbage with a hand blender. Add the yeast flakes and soy sauce. Bring to the boil in a pan. Season to taste with the spices.
Sieve the soup vegetables and add to the finished sauce.
Sieve the beans and add them too. Bring everything to the boil again.
Serve with the finished sweet potatoes and enjoy.