Stroganoff is filled with tender paprika spiced strips of steak. While many US recipes use cream of mushroom soup as the stroganoff base, I prefer to create a more flavorful gravy by deglazing the pan with a dry white wine and adding beef stock, sour cream, Worcestershire and Dijon mustard for a creamy sauce.
Slice the steak into ¼-inch (6mm) wide strips. Season them generously with salt and pepper then toss with the paprika. Heat a large Dutch oven or heavy bottomed pot over medium-high heat, add the vegetable oil and heat through.
Add the steak and sear without moving the meat until golden brown, about 2 minutes. Flip the pieces with tongs and continue to sear on the other side, about an additional 1 to 2 minutes. Remove to a plate and return the pot to medium heat.
Add 4 tablespoons of the butter and allow to melt then add the mushrooms and sauté, stirring occasionally, until golden brown, about 6 minutes. Season with salt and pepper. Add the onion and continue to cook, stirring occasionally until the onions are tender, about an additional 5 minutes.
Bring a large pot of heavily salted water to a boil over high heat. Add the egg noodles and cook until al dente, about 6 to 8 minutes. Drain and add the noodles to a large bowl and toss with the remaining butter to coat.
Add the flour, stirring to coat the mushrooms and onion, cooking until lightly golden brown, about 1 minute.
Pour in the wine to deglaze the pan, then add the beef stock. Bring to a boil until the sauce thickens, about 10 minutes. Whisk in the sour cream followed by the Worcestershire and Dijon.
Stir in the seared beef, then ladle the stroganoff over the buttered egg noodles. Garnish with the parsley and serve immediately.