Chop the onions and tomatoes finely and set aside separately.
Peel and chop the ginger, garlic, and green chillies into smaller chunks. They will get pureed, so no need to chop them finely.
Thaw the frozen spinach by running it under hot water in a colander. Drain the excess liquid after washing. No need to squeeze it dry. You can also thaw it using the microwave.
Puree the thawed spinach, ginger, garlic, green chillies and cloves in a blender. Add a little water if needed to get the blender going.
Heat a large saucepan with 1 tablespoon of oil on medium heat. When the oil begins to shimmer, add the cumin seeds and wait for them to sizzle and turn golden.
Add the chopped onions and saute until they soften
Add the turmeric to the onions.
Add the chopped tomatoes and saute for a couple minutes.
Add half the salt (I like to season in stages)
Add the cumin and coriander powder, and cinnamon, give it a quick stir.
Add the pureed spinach mix. Keep a saucepan lid nearby, since the spinach will bubble and splatter when it hits the hot saucepan.
Once the spinach settles down, remove the cover and stir well. Add the rest of the salt and continue to cook covered for another 8-10 minutes until the spinach loses its bright green color and the oil begins to separate.
Drain the paneer cubes from the hot water and add them to the sauce. Stir to evenly distribute the paneer cubes in the sauce, and simmer on a low fire covered for another 5 minutes to allow the paneer to soak in the sauce. The sauce should be the consistency of marinara sauce, not too runny or too thick. Adjust with cooking for a little bit longer uncovered, or add a little water if it is too thick.
Taste the sauce for spice and salt. This is the time to add extra chilly powder and adjust the salt.
Add the optional garam masala and kasoori methi and serve hot.
Serve with warm naan or basmati rice.