Wash mustard greens and spinach until all dirt is gone. Trim and remove all fibrous material, then chop greens and set aside.
Bring 2 cups water and salt to a boil in a large stockpot. Add mustard greens, spinach, cabbage, and broccoli; cook over medium-high heat until soft, about 10 minutes. Puree with an immersion blender until smooth and creamy.
Combine 1/2 cup water and corn flour in a bowl to make a runny paste with no lumps. Add it to pureed greens and mix until well combined.
Cover and cook over medium-low heat, stirring occasionally, for 10 minutes. Mixture should be a medium consistency and not too runny; add more water if too thick.
Heat oil in a pot over medium-high heat. Add cumin seeds, then add onions and garlic. Saute until onions are translucent, about 8 minutes.
Add tomatoes, chile pepper, coriander, and ginger. Season with salt to taste. Add chickpeas and cook until heated through, about 5 minutes. Gradually stir in cooked greens.