Clean and pat dry the chicken with a paper towel. Slice the chicken in half lengthwise. Set aside.
In a shallow dish: place all the flour mixture ingredients together and mix. Coat each side of the chicken breast with the flour mixture (slowly shake off the extra flour) and set aside.
Set the sauté to high. Add olive oil and butter. Wait until the until the butter has almost completely melted.
Place the chicken in the cooker and cook 3 minutes per-side or until golden brown. Remove the chicken and set aside. You'll have to do this in batches until all the chicken breasts are done.
Add minced shallot, sliced mushrooms and cook for 3-4 minutes.
Add garlic and cook for 30 seconds.
Pour the marsala cooking wine and scrape (deglaze) the bottom of the cooker with wooden spoon.
Add chicken broth, dried thyme and mix.
Return the chicken to the cooker.
Place the lid on. Pressure cook on high for 5 minutes and natural release for 5 minutes. Follow the manufacture instructions for releasing the pressure. Remove the lid. Press cancel and set back to saute on high.
Remove the chicken and set aside.
Add heavy whipping cream, cornstarch mixture (1 tbsp cornstarch + 2 tbsp water) and mix.
Season with salt & pepper to taste. Return the chicken to the cooker. Make sure all the chicken submerges in the sauce. Let simmer for 3-5 minutes or until the sauce thickens to your desired consistency. Garnish with chopped parsley.