To make the sauce, in a small mixing bowl or glass measuring cup, whisk together the chicken broth, soy sauce, worcestershire sauce, fish sauce, and dijon mustard. Set aside.
Turn Instant Pot on SAUTE mode. Once HOT, add oil. Sprinkle the chuck roast with the salt, pepper, and paprika, then add to the pot. Brown on all sides, about 4 minutes per side. Transfer to a cutting board.
Add mushrooms and saute until brown and crispy, about 6-8 minutes, scraping the bottom of pan as you go. Add the onions and saute for 2-3 minutes. Add garlic and saute for 30 seconds, then deglaze with beef broth or au jus. Let simmer.
Cut the steak into 1/2-inch pieces against the grain. Toss with flour. Return to the Instant Pot. Pour the sauce over top.
Place the lid on the Instant Pot, make sure the pressure valve is switched to sealing. Turn Instant Pot on MANUAL (high pressure) for 15 minutes. Let the pressure release naturally (about 12-14 minutes).
Meanwhile, cook the egg noodles according to the package's instructions. Rinse, drain and set aside.
Let the pressure release naturally (about 12-14 minutes).
Open the Instant Pot and slowly. Turn on SAUTE mode. Whisk in the sour cream, taking care not to curdle it.
To thicken the stroganoff, whisk together the cornstarch and cold water in a small bowl and slowly add to the Instant Pot. Let the mixture thicken. Turn Instant Pot off.
Dish up noodles, add sauce over top, then garnish with parsley. Serve immediately.