Cook the Egg Noodles: Bring a large pot of salted water to a boil. Add the egg noodles and cook according to the package instructions until al dente, typically about 7-10 minutes. Drain the noodles in a colander and set aside.

Brown the Ground Beef: In a large skillet, heat over medium-high heat. Add the ground beef, seasoning it generously with salt and pepper. Sauté for about 5-7 minutes until the beef is browned and cooked through. Transfer the meat to a plate.

Sauté the Onions: Drain excess grease from the skillet. Lower the heat, melt butter, and add chopped onions. Sauté for about 2-3 minutes until soft and translucent.

Cook the Mushrooms and Garlic: Stir in the mini portobello mushrooms and cook for 4-5 minutes. Add minced garlic and sauté for another minute.

Prepare the Sauce: Sprinkle flour over the mushroom mixture and whisk in beef broth gradually. Let it simmer for 3-4 minutes until thickened.

Combine Ingredients: Return the ground beef to the skillet with cream cheese, sour cream, and yellow mustard. Stir over low heat until the cream cheese melts and the sauce is creamy.

Toss in the Noodles: Add the cooked egg noodles to the sauce, tossing gently to coat. Cook for an additional minute to warm everything through.

Serve and Garnish: Remove from heat and garnish with fresh parsley. Serve warm and enjoy.