Set Instant Pot to Sauté and heat butter or oil. Brown chicken pieces in batches, seasoning with salt and pepper; remove and set aside.
Sauté onion until soft, then add mushrooms and cook until they release liquid. Stir in garlic, paprika, and flour; cook 1 minute.
Pour in broth, Worcestershire, and Dijon, scraping brown bits. Return chicken to pot. Seal and cook on High Pressure for 6 minutes, then quick release.
Stir in sour cream off heat until smooth. Adjust seasoning and thicken with a cornstarch slurry if needed. Serve over noodles and garnish with parsley.