Wash the spinach thoroughly. Blanch it in water (use little water), then remove the leaves and run in cold water. Retain the water used for blanching.
In a blender, blend together the spinach leaves, ginger, garlic and the green chilli together with the cooking water set aside.
In a pan, heat the butter and add the cumin seeds. Let the cumin seeds splutter.
Add the chopped onions and fry them until brown.
Add the chopped tomatoes, turmeric and chilli powder and fry until the tomatoes are soft.
Add the blended spinach to it and allow it to boil.
Add the salt and panner to this and mix well until the paneer pieces are well coated with the spinach mixture.
Add the cream and serve hot.