In a large skillet over medium heat, add 1 pound of ground beef. Cook until it's browned and no longer pink, breaking it up with a spatula, about 5-7 minutes. Drain excess fat and set the beef aside.

In the same skillet, melt 2 tablespoons of butter over medium heat. Add the chopped medium yellow onion and sauté until translucent, around 3-4 minutes. Stir occasionally to prevent browning.

Stir in the minced garlic and, if using, 1 cup of sliced mushrooms. Cook for about 5-7 minutes or until the mushrooms are nicely browned.

Sprinkle 2 tablespoons of flour evenly over the mixture and stir for about 1 minute. Gradually pour in 2 cups of beef broth while continuously stirring to avoid lumps.

Stir in 1 tablespoon of Worcestershire sauce and simmer for about 5-7 minutes, stirring occasionally to thicken the sauce.

Return the cooked beef to the skillet, gently stirring it back into the sauce. Mix in 1 cup of sour cream, allowing it to melt for about 2-3 minutes without boiling.

While the sauce simmers, cook 8 ounces of egg noodles according to package instructions. Drain and set aside.

Fold the drained noodles into the creamy beef mixture gently until fully coated. Season with salt and pepper to taste and serve warm, garnished with fresh parsley if desired.