Reserve the stems of coriander leaves. Heat oil in a pan. Add onion, spring onion bulb, ginger and garlic and sauté till translucent.
Add gram flour and continue to sauté till you get a nice aroma. Add vegetable stock, coriander stems, cabbage and carrot cubes and bring to a boil.
Add crushed peppercorns and continue to boil. Add half of the chopped coriander leaves and cook for five to ten minutes.
Strain and keep aside cooked vegetables. Heat the strained soup. Add salt, lemon juice and bring to a boil again. Season with the remaining chopped coriander leaves and serve hot.