First make the marinade. Combine the yoghurt, tomato puree, salt turmeric and chilli powder in a bowl and mix well. Add the paneer and stir so that the cubes are well covered in the marinade. Cover the bowl with clingfilm and set aside for an hour.
Meanwhile start making the sauce. Heat the sunflower oil in a wide saucepan over a medium heat. Add the cumin and carob seeds and cook until they begin to sizzle. Mix in the ginger and garlic and cook for 1 minute, then stir in the onion and chilli and cook, stirring occasionally, for 8-10 minutes until the onion turns golden brown.
Add the tomato puree, salt, chilli powder, ground coriander, garam masala and 200 ml water to the pan. Stir well, then cover and reduce the heat to low. Cook for 10-15 minutes until cooked through. Remove from the heat and set aside.
When the paneer has finished marinating, heat the oil in a frying pan. Lift the cubes from the marinade and fry in batches for about 2 minutes, turning to colour them evenly, until golden brown. Transfer to the sauce as you finish each batch.
When all the paneer is cooked and added to the sauce put the sauce back on the hob over a medium heat. Stir in the kasuri methi and double cream, and cook for 5 minutes until heatd through. Serve hot with rice or naan.