Chop the spinach roughly. If using baby spinach, you can forego this step.
Make the ginger-garlic paste - put 8-10 garlic cloves and an inch long piece of ginger in a blender along with a few tablespoons of water and blend. If making the exact amount needed for this recipe, you can throw in the cashews too for convenience. No need to puree them separately.
However, if you want to make a larger batch of ginger-garlic paste to use later, you will need to puree the cashews separately. Just soak the cashews in a little warm water for 15 minutes and blend along with the water to get a smooth puree.
Cooking on the stovetop
Heat oil in a pan and add the whole spices. When they change colour, add onions and fry until they caramelize and turn reddish brown.
Add the ginger-garlic paste, cashew paste, chopped tomatoes, powdered spices and salt. Saute for 8-10 minutes on low to medium heat or until the masala is thick and shiny. Add water as required to keep the masala from burning.
Add the chicken pieces, 1 cup water and cook on slow heat until tender. Add more water as required.
Add the chopped spinach leaves and cook for 2 minutes more. Serve palak chicken with Indian bread or rice.
Cooking in the instant pot
Switch on your instant pot to sauté and add the cooking oil. Wait for it to display HOT, then add the whole spices. When they start to sizzle (a few seconds), add the onions and fry until golden brown (approx. 8-10 minutes).
Add the ginger-garlic paste, cashew paste, chopped tomatoes, salt and powdered spices. Sauté until the masala is thick and shiny and the oil leaves the sides (8-10 minutes). Cancel sauté.
Add the chicken pieces and 1 cup water. Secure the lid, make sure the steam release handle is on 'sealing' and press the pressure cooking button. Adjust it to high and set the timer for 5 minutes.
When the timer beeps, wait for 5 minutes, then release pressure by turning the steam release handle to 'venting'. Switch back to sauté and add the spinach leaves. They will wilt very quickly. Let the spinach cook in the chicken masala for 2 minutes until it is well mixed with the masala. Serve hot with Indian bread or rice.
The gravy in palak chicken is supposed to be thick. Spinach releases a lot of water, so if you find the gravy getting watery after you've added it, just cook on high heat until most of the liquid gets absorbed.
Spinach is quite salty on its own, so be careful while adding salt. You might not need to put in as much as you do in other dishes.
You can adjust the red chilli powder too according to your taste. If one teaspoon is too much, reduce the quantity to half.
If you don't have the whole spices required for this recipe, you can substitute with powdered garam masala. It is available easily in Indian stores and the international aisles of most supermarkets.