Heat the Instant Pot and pour the oil and butter into it. Let the butter melt.
Add the cumin seeds and wait until it splutters. Then add the green chillies and ginger-garlic paste. Sauté for a few seconds.
Next, add in the onions and sauté until it becomes translucent.
Transfer the cubed tomatoes and the salt. Let it cook for a minute.
Quickly add the turmeric powder, chilli powder, coriander powder. Drop in the cashew nuts.
Give it a mix and add the water. Cover and seal with the Instant Pot lid. Pressure cook for 8 minutes.
Quick release after the cook time and open the Instant Pot. Using a hand held blender, blend the cooked mixture until smooth and no visible chunks are seen. *
Pour in the milk into the curry base. Add the garam masala powder, sugar and the kasuri methi leaves. Give it a thorough mix.
Add the Paneer and the peas. Gently mix to coat.
Cover with the Instant Pot lid and SEAL it. PRESSURE COOK for 5 minutes.
Quick Release, remove the lid and serve it right away!
Milk: With minimal addition of water/liquid the thickness of the curry comes out just perfect using milk. I don't see any need for heavy cream at all. But if you want to go for the richest or you have excess heavy cream you can use the same quantity of heavy cream in place of milk.
Blending: The cooked mixture has to be blended until smooth. Ensure there aren't any visible solids by stirring through with a slotted spoon.
Chilli Powder: I use regular chili powder for this curry. But if you like a bit more of an orangish color, go for Kashmiri Chilli Powder or chili powders labeled as dark. In that case, use 1.5 tsp of Kashmiri chili powder.
Hotness and sweetness: This gives a spicy but sweetish curry. That's how this curry is supposed to be. But you can reduce or skip the added sugar or you can reduce or increase the quantity of chili powder.
Storing: This curry tastes the best when served immediately. Paneer tends to get hard when refrigerated and it does not freeze well. If you would like to make this ahead, stop with the first stage of PRESSURE COOKING, blend and freeze in an airtight container once it cools down. To reuse, thaw it overnight or place the container in warm water. Dump this and all the ingredients mentioned in the second stage and cook.
Paneer: You can either add the paneer directly or shallow fry them in a nonstick pan and then add them to the curry.
You can also use fresh peas in place of frozen green peas. In that case, you will have to blanch the peas in hot water for 2-3 minutes before adding to the Instant Pot.