1. In a pressure cooker, add mustard green, spinach, water, ginger, garlic, green chillies and salt. Mix well and let the spinach leaves wilt for a few minutes. Cover the pressure cooker with a lid and let the green cook for about 5 - 6 whistles. Once done, set the cooker aside to lower the pressure inside the cooker naturally.
2. In a saute pan on medium low, heat oil and ghee and pan fry the paneer cubes gently until light golden brown and crisp. Once done transfer it onto a plate and set aside.
3. In the same heated pan, add cumin seeds, hing, turmeric powder, onion and salt. Mix well and stir fry the onions for a few minutes until the turn golden brown.
4. Once the onions turn light golden brown, add coriander cumin powder and garam masala. Stir fry for a few seconds.
5. Once the pressure inside the cooker has reduced, open it and using a hand blender, blend the mixture until the puree is thick and smooth.
6. Pour this puree into the onion masala mixture and add the corn flour. Mix until well combined and let the mixture cook for 4 minutes.
7. Switch off heat and get ready to serve.
8. Serve this sarson ka saag with makai ki roti or paratha.