Select sauté on the instant pot and adjust to normal.
Add oil to the pot.
When the pot is hot, add the chopped onions and keep stirring to prevent the onions from burning.
Add the ginger garlic paste and stir well.
Add the chopped chicken, sauté for about 4 to 5 minutes to eliminate the pink color. Keep stirring.
Add the tomato puree and let it sauté for a minute.
Add the red chili powder (cayenne pepper), ground pepper, ground cumin, ground coriander, salt, and garam masala. Stir well.
Scrape off the sides and bottom to make sure nothing is stuck on the sides or bottom.
Secure the lid on the pot and close the pressure-release valve.
Select manual and cook at high pressure for 8 minutes.
Meanwhile, add ¼ cup water to the toasted walnuts in a blender/ coffee blender and puree the walnuts.
When cooking is complete, use quick release to depressurize.
Open the lid. Select sauté. Add the pureed walnut and half and half. Let it sauté for about a minute and stir. Press cancel.
Transfer to a bowl immediately.