01 - Bring a large pot of well-salted water to a rolling boil. Add the egg noodles and cook according to package directions until al dente. Drain thoroughly and set aside.
02 - While the noodles cook, heat olive oil in a large skillet over medium-high heat. Add the ground beef and cook, breaking it apart with a wooden spoon, until fully browned and no pink remains. Transfer the beef to a plate using a slotted spoon, leaving drippings in the pan.
03 - In the same skillet, add the diced onion and cook for 3 to 4 minutes until softened and translucent. Add the sliced mushrooms and continue cooking for 5 minutes until golden brown. Stir in the minced garlic and sauté for 1 minute until fragrant.
04 - Add the butter to the skillet and allow it to melt into the vegetables. Sprinkle the flour over the mixture and stir continuously for 1 to 2 minutes to cook off the raw flour taste.
05 - Gradually pour in the beef broth while whisking constantly to prevent lumps from forming. Stir in the Worcestershire sauce and Dijon mustard. Bring the mixture to a gentle simmer and cook for 5 minutes until the sauce thickens slightly and coats the back of a spoon.
06 - Return the browned beef to the skillet and stir to incorporate. Reduce the heat to low, then gently fold in the sour cream until the sauce is smooth and creamy. Season generously with salt and black pepper to taste.
07 - Add the drained egg noodles to the skillet and toss gently until evenly coated with the stroganoff sauce. Serve immediately, garnished with chopped fresh parsley.