Begin by preparing the egg noodles according to package instructions in a large pot of salted boiling water. This takes about 7–10 minutes until they are tender.

In a large skillet, add the ground beef over medium-high heat, breaking it apart while cooking. Season with salt and pepper for about 5–7 minutes until browned. Drain excess fat.

Melt the butter in the skillet and sauté the diced onion for 2–3 minutes until translucent.

Stir in the sliced mushrooms and cook for 5 minutes. Add minced garlic during the last minute.

Sprinkle flour over the mixture, then gradually pour in beef broth while stirring to avoid lumps until thickened.

Return the browned ground beef, cream cheese, sour cream, and mustard to the skillet. Stir until smooth.

Add drained egg noodles and toss to coat in the sauce. Cook for an additional minute to meld flavors.

Remove from heat and garnish with parsley if desired. Serve immediately.