Add 1 teaspoon salt, pepper, oregano, thyme and flour to a zip lock bag. Mix well and add chicken breasts to the bag. Shake the zip lock back few times so chicken gets coated with the flour.
Turn Instant Pot to saute and heat 1 tablespoon of butter. Add mushrooms and saute them for 2 to 3 minutes until they cook dark brown and the liquids start to evaporate. Take the mushrooms out and reserve.
Add remaining butter, line the chicken breasts. Cook for a minute. Flip the chicken breasts on the other side. Add onions, marsala wine and 1 teaspoon salt, mix well and cook for another minute as some of the wine starts to evaporate and reduce. Deglaze the bottom of the pot well to remove any stuck bits.
Close the Instant Pot lid with pressure valve to sealing. Pressure Cook for 5 minutes and allow 10 minute natural pressure release.
Open the Instant Pot and set to saute mode. Stir in the reserved mushrooms, simmer for 3 to 4 minutes as the sauce thickens to get it to desired consistency. Sauce will also thicken as it cools down. Garnish with parsley.
Add 2 to 3 tablespoons of heavy cream for a rich, creamy sauce.
Substitute shiitake or cremini mushrooms with your favorite mushrooms. You can also use 4 cups of white mushrooms.