Put the oil into a pan, place over a medium heat and when it’s hot, seal the paneer on all sides until golden. It will spit, so keep the pan loosely covered, using the lid as a shield to protect you from the oil.
Remove the paneer with a slotted spoon, then toss the onion, ginger and garlic into the pan. Cook for five minutes until they soften and start taking on colour, then add the cumin seeds, green chilli, turmeric and chilli powder and sauté for another five minutes.
Roughly slice and add the greens, along with 500ml of hot water and the salt. Let the greens cook, uncovered, until they wilt, then turn off the heat.
When the contents of the pan have cooled sufficiently for your food processor or blender, tip the greens in and blitz to a smooth paste with the remaining 125ml of water (or use a hand blender.) You should get a thick, creamy and bright green mixture.
Pour the saag back into the pan and place over a medium heat. Drop the paneer in, along with the garam masala or fenugreek leaves. Warm the mixture for five minutes until the paneer softens and bubbles start appearing.
Scoop into a bowl and finish with a swirl of single cream and a few coriander leaves. Serve with lemon or lime to squeeze over.