Close the lid. Set the steam release knob to the Sealing position.
Press the Manual (or Pressure Cook) button or dial and then the + or - button or dial to select 8 minutes.
After cook cycle ends, let the pot naturally release the pressure for 8 minutes. Then manually release the remaining steam and open the lid.
Use a slotted spoon to take out the chicken, and set it aside in a bowl covered with foil.
Use an immersion blender to make the sauce really smooth. You could use a blender if you want. Either way, be very careful since the contents are so hot!
Add remaining 1 teaspoon of Garam Masala and the remaining 2 Tbsp of butter. Stir until butter is melted.
Add the heavy cream & coconut milk cream if using, and the chicken, and stir until combined. Taste and adjust salt if necessary.
Serve over rice, or with naan, and garnish with cilantro leaves and toasted cashews (optional).