Blanch the spinach in boiling water for 3 minutes, or until wilted. Drain the spinach into a colander and run cold water over it until cool. In a food processor or blender, blend to a smooth paste, and set aside.
Heat the oil in a large nonstick pan. Add the cumin and fry for about 30 seconds, or until fragrant, then add the onion and fry over a low heat for about 6 minutes, or until the onions are soft. Add the ginger, garlic, and chiles, and cook for another minute.
Add the ground coriander, and salt, to taste. Cook for another 30 seconds, then add the spinach and a splash of water, if necessary. The mixture should be loose, but not watery. Bring the mixture to a boil, and then simmer for 3 minutes.
Add the paneer cubes, garam masala, and milk to the pan. Stir the mixture, and cook for a few minutes, or until the spinach is nice and creamy. Stir in the lemon juice, to taste. Transfer the mixture to a warmed dish and serve with rice pilaf or naan bread.