Put the tomatoes, onions, coriander seeds, green chillies, and cashews in a big enough sauce pot.
Add enough water to cover the vegetables and let it come to a boil.
Drain the water and blend it to a paste.
Take a pan and heat the butter. Once hot, add in the ginger-garlic paste. Fry till golden.
Add the onion-tomato paste.
Fry on medium heat for about 15 minutes, or until the oil separates.
Add salt and turmeric powder, chilli powder and let cook for another 15-20 minutes on medium-low flame.
Add ¼ cup of the warm water. Cook for 5 minutes and keep adding the rest of 1 cup of water every 5 minutes, for the next 15 minutes.
Add the roasted cumin powder and fenugreek leaves to the sauce and mix well. Season with salt. Add the ketchup. The ketchup adds a little sweetness and gives the gravy a reddish colour- you're welcome to leave it out.
Meanwhile, saute the paneer with a little butter.
Add the paneer to the sauce and cook for 2-3 minutes. Add finely chopped cilantro, the milk and if required a little more warm water.