First, set the cooked chicken aside in a bowl. Peel and dice the onion, peel and cut the carrots, and cut the celery and mushrooms into thin slices. Peel and mince the garlic. Rinse the rice in a fine mesh strainer under cold water.
Turn on the Instant Pot to Sauté mode. When the pot is hot, add the oil and wait for it to shimmer. Then, add the onions, celery, carrots, mushrooms, and garlic and sauté for 3-4 minutes, until the vegetables are slightly softened.
Add the broth, rice, seasonings and cooked chicken. Stir, then close and lock the Instant Pot lid. Turn the pressure valve to "Sealing", then manually set to cook at High pressure for 3 minutes.
After the 3 minutes are done, allow for a natural pressure release (NPR) for at least 10 minutes. Turn the pressure release valve to release any remaining steam, then carefully open and remove the lid.
Taste the soup and season with additional salt and pepper if desired. Ladle into bowls and serve while warm.
Video
Notes
To use raw chicken, use 1 pound of boneless skinless breasts or thighs. You do not need to adjust the cooking time. Cut the chicken into bite-sized pieces and sauté it in the Instant Pot with the vegetables.
To store leftovers: Transfer room temperature soup to an airtight container or Ziploc bag and store in the refrigerator.
The soup tastes best when reheated and eaten within 24 hours, but it will keep for up to 5 days. The rice will continue to absorb liquid over time, so you may need to add a bit more chicken broth to thin it out before reheating.
*Instructions to make chicken and wild rice soup in a crock pot are noted in the post.