Prepare the spinach: Blanch the washed spinach leaves in boiling water for 2-3 minutes until wilted. Immediately transfer the spinach to an ice bath (a bowl of cold water with ice cubes) to stop the cooking process and preserve its vibrant green color. Once cooled, drain the spinach thoroughly and blend it into a smooth purée using a blender or food processor. Set aside.

Heat the ghee or oil in a large pan or Dutch oven over medium heat (180°C / 350°F). Once shimmering, add the cumin seeds and let them splutter for about 30 seconds until fragrant. Be careful not to burn them.

Add the finely chopped onion to the pan. Sauté the onions, stirring occasionally, for about 8-10 minutes until they are softened and translucent, and start to turn golden brown at the edges. This caramelization adds depth of flavor.

Stir in the grated ginger and minced garlic. Cook for another 1-2 minutes until their raw aroma disappears and they become fragrant. Add the chopped green chilies if using, and sauté for 30 seconds more.

Add the pureed tomatoes to the pan. Cook, stirring frequently, for about 5-7 minutes, until the tomatoes are well cooked, the oil starts to separate from the mixture, and the sauce thickens. This indicates that the raw tomato flavor has cooked out.

Add the ground spices: turmeric powder, coriander powder, garam masala, and red chili powder (if using). Stir well to combine with the tomato-onion mixture. Cook for 1 minute, stirring constantly, until the spices are fragrant. This step is called 'bhunai' and is crucial for developing flavor.

Pour in the spinach purée and add the salt. Stir everything together to combine thoroughly. Bring the mixture to a gentle simmer.

Add the water (start with 120ml or 0.5 cup) to achieve your desired gravy consistency. Stir well and let the sauce simmer gently for about 5-7 minutes, allowing the flavors to meld. If the sauce becomes too thick, add a little more water.

Gently add the paneer cubes to the simmering spinach gravy. Stir carefully to coat the paneer without breaking it. Allow the paneer to simmer in the sauce for 3-5 minutes, just enough to heat through and absorb some flavor. Overcooking can make paneer tough.

Stir in the heavy cream or cashew cream. Mix gently until the sauce is smooth and creamy. Cook for another 1-2 minutes on low heat, just until the cream is incorporated and the sauce is heated through. Do not boil after adding cream.

Crush the Kasuri Methi (dried fenugreek leaves) between your palms and sprinkle it over the curry. This adds a distinct aroma and flavor. Stir it in gently.

Taste and adjust seasoning if needed, adding more salt or garam masala. Serve the Palak Paneer hot, garnished with a swirl of cream or a dollop of ghee, if desired.