To a large ziplock bag add flour, salt, pepper and parsley and mix well.Add chicken pieces, seal and shake to coat the chicken well with the flour mixture. Set aside. Add olive oil to Instant Pot, press SAUTE mode and let pot heat up until screen reads HOT.Add the chicken pieces and cook 3 minutes on each side. Set aside the remaining flour mixture in bag. Transfer chicken to a plate and set aside. Add butter to the pot and then the chopped onion, and cook 3 minutes until softened.Add garlic and the remaining flour mixture you had set aside earlier. Stir and cook 1 minute more.Press CANCEL. Add broth, lemon juice and thyme and stir together well, scraping bottom of pot to loosen up any browned bits.
Add chicken, turning each piece once over to coat with liquid.Lock on lid, turn pressure valve to SEALNG.Choose PRESSURE COOK and adjust timer to 7 minutes. When cooking time is up allow pot timer to count up 10 minutes for natural pressure release.
Press CANCEL.Carefully turn pressure valve on lid to VENTING and allow any remaining pressure to release, then open lid and transfer chicken to a plate. Press SAUTE mode.Add 2 tbsp butter, stir and let mixture cook for a few minutes until reduced by 1/2.Press CANCEL. Return chicken to pot, lock on lid and let chicken rest and keep warm until ready to serve.
Serve chicken topped with the sauce.