Cook the Egg Noodles – Bring a large pot of salted water to a boil and cook the egg noodles according to the package instructions (usually 7-9 minutes). Drain and set aside.
Brown the Ground Beef – In a large skillet over medium heat, cook the ground beef until browned and fully cooked (about 5-7 minutes). Break it up with a wooden spoon as it cooks. If there's excess grease, drain it.
Sauté the Onions and Mushrooms – Add the butter to the same skillet, then toss in the diced onions and sliced mushrooms. Cook for about 4-5 minutes until they soften and start to caramelize. Stir in the minced garlic and cook for another 30 seconds until fragrant.
Pro Tip: Don’t rush this step! Let the mushrooms brown properly for the best flavor.
Make the Sauce Base – Sprinkle the flour over the mushroom and onion mixture, stirring well to coat everything evenly. Cook for 1 minute to remove the raw flour taste.
Add the Broth and Seasonings – Slowly pour in the beef broth while stirring constantly to prevent lumps. Add the Worcestershire sauce, Dijon mustard, salt, and black pepper. Bring the mixture to a gentle simmer and let it cook for 3-5 minutes until slightly thickened.
Pro Tip: Whisk continuously as you add the broth to ensure a smooth, velvety sauce.
Stir in the Sour Cream – Reduce the heat to low and gently mix in the sour cream until smooth and creamy. Let it warm through for 1-2 minutes but don’t let it boil, or it might curdle.
Combine with Noodles – Add the cooked egg noodles to the skillet and toss everything together until the noodles are well coated in the sauce. Cook for another minute to let the flavors meld.
Serve and Enjoy – Garnish with fresh chopped parsley if you’d like, and serve hot. Pair it with a side of steamed veggies or a simple salad for a complete meal.