Using a very sharp knife, carefully butterfly Chicken Breasts and then cut into two equal pieces. Place each piece of Chicken between plastic wrap or waxed paper and lightly pound, until thin and even.
In a shallow dish, mix together Potato Starch, Salt and Pepper. Dredge Chicken through Potato Starch mixture and shake off all excess Starch. Cutlets should only have a light dusting of Starch.
Select Sauté/Browning and adjust to High. Allow pot to fully heat and then add Oil. When Oil is hot, in batches, place Chicken Cutlets into cooking pot and Sear on each side. Remove Cutlets to a plate lined with a paper towel.
Adjust Pressure Cooker to Normal and add diced Prosciutto. Pour in 1/4 cup of the Marsala Wine and scrape the bottom of the pot to deglaze. Continue to cook Prosciutto to render fat.
When liquid has reduced and the Prosciutto begins to brown, melt in Butter. Add 1/4 cup Marsala, Mushrooms, Shallots/Onions and Sauté until Shallots/Onions are soft and liquid is syrupy, about three minutes. Mix in the Garlic.
Pour in the rest of the Marsala Wine and allow to bubble and reduce, for a couple of minutes. Turn off Pressure Cooker and add Chicken Stock, Herbes de Provence and Thyme. Return Cutlets to pot.
Lock on lid and close Pressure Valve. Cook at High Pressure for 2 minutes. When Beep sounds, wait 5 minutes and then release pressure. Plate and Garnish with Parsley.
Notes
Wild Mushrooms can be used.Use a good Dry Marsala Wine, one that you would enjoy drinking, for this recipe. Marsala Wine labeled "Cooking" Wine is not recommended.It is important to make sure to shake off all excess Potato Starch, so that you won't have a gummy Sauce.1/4 teaspoon of Ground Thyme can be used in place of Fresh Thyme.