Heat oil in a large skillet or Dutch oven over medium heat. Add cumin seeds and allow them to sizzle for a few seconds.
When the cumin becomes fragrant, add the prepared onion-tomato paste. Also add the ginger-garlic-green chili paste. Add turmeric, coriander powder, Kashmiri red chili powder, garam masala, and salt. Mix well. Cover and let it cook on a low flame. Mix every couple of minutes to make sure the masala doesn't stick to the pot.
Cook until the gravy base becomes brown and oil separates.
This step is important because allowing the tomato-onion mixture to cook properly gives the curry much more depth of flavor.
Add the spinach puree. Stir everything together and simmer gently until the spinach gravy has thickened. This should take about a minute.
Avoid boiling the spinach aggressively for a long time. A gentle simmer is all you need. Now add the air-fried potatoes
Add crushed kasuri methi and finish with a drizzle of cream. Turn the stove off.
Taste and adjust the salt, spice, and consistency as needed.