Thaw the frozen spinach in the microwave for 7 minutes on high, or until well thawed. Let cool for about 10 minutes.
Put the thawed spinach into a food processor. Add the tomato, flour, ginger, ground coriander, cayenne powder and turmeric. Puree.
In a large nonstick frying pan put the oil and heat over medium-high heat. When the oil is hot, add the cubed paneer cheese and cook until well browned. Place the cheese on paper towels to drain and set aside.
Remove half the remaining oil in the frying pan. Reheat the pan over medium heat. When the oil is hot, add the spinach mixture and stir-fry for about 10 minutes until everything is well cooked.
Add the salt and garam masala (optional) and stir to blend.
Remove pan from the heat and stir in half the cream, milk or yogurt (or a combination, or leave out entirely). When well blended, add the rest of the cream, milk or yogurt and mix again. Add extra dairy if you like it creamier.
Put the frying pan back on the heat. Stir in the fried cheese and cook just until the curry is heated through.
Good served with either rice or Indian bread. Also delicious adding a bit of it to an omelet.
Variations: Instead of paneer cheese, you could add diced potatoes, chickpeas, or frozen green peas stirred in at the end. You may also serve the spinach plain without the cheese, potatoes, chickpeas or peas.