Heat mustard oil in a pan. Mustard oil has a very strong flavor. Therefore, to get rid of that pungent flavor, cook mustard oil to its smoking point and take it off the flame. Let it cool.
When ready to make the masala – slightly warm the mustard oil and add whole spices and cumin seeds to the pan.
As the seeds start to crackle, add onion and ginger-garlic paste. Mix to combine. Sauté for 3-4 minutes until the oil starts to separate.
Stir in the tomato puree. Mix to combine.
Stir in all the spices - coriander powder, chili powder, kasoori methi, garam masala, and salt. Mix until combined.
Cook the tomatoes for another 3-4 minutes or until the oil separates.
Pour in the blanched spinach puree. Stir to combine.
Add chicken pieces to the blanched spinach. Cook for another 3-4 minutes on medium-low heat, stirring occasionally.
Finally, add the cream. Give it a gentle stir and take it off the flame.
Serve hot with warm rotis, naan or white rice.