Add chicken in a bowl with all the marinate ingredients. Mix well and refrigerate it for 30 minutes (or up to 8 hours).
Add the milk to a small bowl and warm it in the microwave. Add the saffron strands to it. Keep aside. Start the instant pot on sauté mode and heat it. Add ghee, and then the cashews, raisins and saute them for about a minute until they are lightly golden. Take out and reserve for later.
Add in the sliced onions. Cook them for about 10-12 minutes until onions caramelize. Stir frequently, so they don't stick to the bottom. Take out half of the caramelized onions.
Add the whole spices and saute for 30 seconds. Add the marinated chicken. Mix well and saute for about 3 minutes minutes. Make sure to deglaze the pot well. Then spread the chicken evenly on the base of the pot.
Spread the rice evenly over the chicken. Spread the saffron soaked in milk on top of the rice. Then add the 1 cup of water to the pot. Close the lid with vent in sealing position.
Change the instant pot setting to manual or pressure cook mode at high pressure for 4 minutes. When the instant pot beeps, do a 10 minute NPR. Let the pressure release naturally for 10 minutes, then quick release the pressure manually.
Garnish with the reserved caramelized onions, cashews and raisins. Garnish with chopped cilantro leaves. Serve chicken biryani with raita.