Season both sides of chicken thighs with the salt, onion powder, paprika, and black pepper. Turn pressure cooker onto the saute function and heat up inner pot until hot. Add olive oil and sear chicken 2-3 minutes on each side.
Spread chicken to the perimeter of the pot and add sliced mushrooms to the center. Stir mushrooms around a bit for two minutes, then stir together with the chicken. Cancel the saute function.
Add chicken broth and stir to mix with chicken and mushrooms. Secure lid, ensuring the pressure valve is pointed toward sealing. Select pressure cook (or manual) and set the time to 7 minutes. When the cooking cycle is complete, let sit another 5 minutes then turn the valve to release the pressure.
Remove lid. Using tongs, transfer all chicken pieces to a plate and cover with foil. Turn on saute function and simmer broth/mushroom mixture for 5 minutes.
Whisk slurry mixture (2 tablespoons corn starch blended with 2 tablespoons water) into broth. Whisk until thickened, approximately 1-2 minutes. Pour heavy cream into broth mixture and stir well. Add cooked chicken pieces and mix until chicken is fully coated in creamy mushroom gravy. Heat through another minute then turn off saute function. Serve over rice and garnished with chopped parsley.