Set your Instant Pot to the sauté mode and add olive oil and butter. Once hot, add diced onions, celery, carrots, and minced garlic. Sauté until vegetables are softened, about 4-5 minutes.

Add thinly sliced mushrooms to the pot and continue sautéing until they release their moisture and start to brown, about 5-6 minutes.

Stir in dried oregano, dried thyme, and flour, coating the vegetables evenly. Cook for another minute to remove the raw flour taste.

Pour in chicken broth and deglaze the bottom of the pot to ensure no bits are stuck. Add chicken breasts or thighs to the pot.

Close the Instant Pot lid, seal the vent, and set to pressure cook on high for 10 minutes. Once the cooking time is complete, allow for a natural pressure release for 10 minutes, then carefully perform a quick pressure release.

Open the lid and remove the chicken from the pot. Shred or chop the chicken into bite-sized pieces and return it to the pot.

Stir in heavy cream and season with salt and black pepper to taste. Let the soup simmer for a few minutes until heated through and slightly thickened.

Serve hot, garnished with fresh herbs if desired. Enjoy your delicious Instant Pot Creamy Chicken Mushroom Soup!