Press the SAUTE button on Instant Pot. Heat the oil and melt the butter.
Season the chicken with salt and pepper, and cook cook each side for 2-3 minutes, or until light golden brown color. Remove chicken and set to side.
Add minced garlic to the pot, and cook for 30 seconds or until fragrant.
Add chicken/vegetable stock and deglaze the pot by removing any bits stuck to the bottom of the pot. Be sure to remove all bits from bottom or you will get the dreaded BURN message.
Add Italian seasoning, salt, pepper, and chili flakes.
Secure the lid and set the vent to SEALING. Select the PRESSURE COOK/MANUAL setting and set the cooking time for 5 minutes at high pressure. The Instant Pot will take around 6-7 minutes to come to pressure and start cooking. Once cooking time is done, quickly release the steam.
Carefully remove the lid, take the chicken out of the pot onto a plate and set aside.
Choose the SAUTE setting, stir in the heavy cream and the freshly grated parmesan.
Add chopped sundried tomatoes, and spinach leaves to the pot. Switch off the SAUTE setting, and allow the spinach leaves to wilt.
Put the chicken back in, and spoon the cream sauce over it. Serve over buttered pasta or rice with extra grated parmesan cheese.