Season chicken with salt and pepper to taste. Set aside.
Rinse rice with cold water and drain thoroughly.
PRESS the SAUTE mode button on the Instant Pot. When HOT appears on the display, add oil and heat with the Instant Pot lid open.
Add onions and cook until softened.
Add mushrooms and cook, stirring occasionally, until lightly browned and liquid dispelled is absorbed.
Add the chicken broth and using a wooden spoon, scrape the bottom of the pot to deglaze.
Add rice, dried parsley, and about 1 teaspoon salt. Stir to distribute.
Arrange chicken breasts in a single layer on top of the rice mixture.
Press KEEP WARM/CANCEL button. Close and lock the lid, making sure the floating valve is set on SEALING. Set at HIGH pressure and adjust the cooking time to 5 minutes.
After the 5 minutes and the Instant Pop beeps, allow natural pressure release (set for 10 minutes. Then turn the steam floating valve on the lid to the VENTING position to release the remaining pressure manually. Carefully open lid.
Shred the chicken with two forks and gently fluff the rice to distribute. Serve hot.