Put the paneer in a bowl with the turmeric, Kashmiri chilli powder, salt and 10ml oil. Fold gently until evenly coated. Cover and leave at room temperature for 30 minutes.
Heat 20ml oil in a wide sauté pan over medium high heat. Add the paneer in one layer and fry for 3 to 4 minutes, turning until two or three sides are golden. Transfer it to a plate before it becomes firm.
If using fresh spinach, blanch it in a large pot of boiling water for 60 to 90 seconds, working in batches if necessary. Transfer it immediately to iced water, then drain and squeeze out the excess liquid. If using frozen spinach, squeeze it thoroughly after thawing. Divide the drained spinach into two equal portions. Blend one portion to a coarse purée and finely chop the other. If the blender blades will not turn, add up to 15ml of the measured hot water and subtract that amount from the water available in Step 7.
Bring the base sauce to a gentle simmer in a separate saucepan. Wipe loose spices from the sauté pan, then heat 20ml oil or ghee over medium high heat. Add the cumin seeds and fry for 30 seconds, until aromatic.
Add the Garlic and Ginger Paste and stir continuously for 45 seconds. Add the tomato purée, Mixed Powder and Kashmiri chilli powder with 30ml hot water. Cook for 90 seconds, stirring, until the tomato darkens slightly and the oil begins to show around the edges.
Add 100ml hot base sauce and let it bubble for 2 minutes, scraping caramelised sauce from the sides of the pan. Add the remaining 100ml base sauce and simmer for 3 to 4 minutes, until it coats the back of a spoon.
Stir in the blended and chopped spinach, kasoori methi, Garam Masala and salt. Cook uncovered for 4 to 5 minutes, stirring often, until hot and thick. Add the remaining hot water in 15ml additions only if the sauce becomes too thick.
Fold in the fried paneer and simmer gently for 2 minutes. Reduce the heat to low and stir in the cream until evenly combined.
Remove the pan from the heat and stir in the lemon juice. Taste and add more salt if needed. Rest for 5 minutes before serving.