01 - Bring a large pot of salted water to a rolling boil. Cook egg noodles according to package directions until al dente. Drain thoroughly and set aside.
02 - Melt butter in a large skillet over medium-high heat. Add chopped onions and cook for 2-3 minutes until softened. Add sliced mushrooms and continue cooking for 4-5 minutes until mushrooms release moisture and begin to brown.
03 - Stir in minced garlic and cook for 30 seconds, constantly stirring to prevent burning.
04 - Add ground beef to the skillet. Break apart with a wooden spoon and cook for 5-7 minutes until fully browned and cooked through. Drain excess fat if needed.
05 - Sprinkle flour evenly over the meat mixture. Stir thoroughly to coat all ingredients. Cook for 1 minute to eliminate raw flour taste.
06 - Slowly pour in beef broth while stirring. Add Worcestershire sauce and Dijon mustard. Bring to a gentle simmer, scraping browned bits from skillet bottom. Season with salt and pepper.
07 - Reduce heat to low and simmer for 5-7 minutes until sauce slightly thickens.
08 - Remove skillet from heat. Gradually fold in sour cream until completely incorporated and sauce reaches creamy consistency.
09 - Taste and adjust seasoning as desired. Plate stroganoff over prepared egg noodles. Garnish with fresh parsley if using.