Combine besan, curd and turmeric powder and mix them until no lumps are left.
Heat oil in non-stick pan and add cumin seeds.
Add green chillies, ginger and cook on a low flame for 10 seconds.
Add onions and cook for approx 2 minutes.
After this, add the mixture you had prepared earlies along with half cup water and milk. Mix them well and cook on low flame for 4 minutes and keep on stirring occasionally.
Add tomatoes, cucumber and salt and saute for another minute.
The soup is ready, garnish it with coriander and serve immediately.