Bring a large pot of salted water to a boil. Cook the egg noodles according to package instructions, usually about 7-9 minutes, until al dente. Drain and set aside, tossing with a tiny bit of olive oil to prevent sticking.

In a large skillet, cook the ground beef over medium-high heat. Use a wooden spoon to break it into small crumbles. Once fully cooked, remove the beef with a slotted spoon and set aside, leaving about 2 tablespoons of fat in the pan.

Add a tablespoon of butter to the skillet. Toss in the diced onions and sliced mushrooms. Cook until the mushrooms are golden brown. Stir in the minced garlic and thyme during the last minute.

Sprinkle the flour over the vegetables and stir constantly for about two minutes to cook out the raw flour taste.

Slowly pour in the beef broth while whisking or stirring vigorously to prevent lumps. Add the Worcestershire sauce and Dijon mustard. Bring to a gentle simmer and let it bubble until it begins to thicken, usually about 5 minutes.

Stir the cooked ground beef back into the sauce. Lower the heat to low. Stir in the sour cream until the sauce is a beautiful, pale tan color. Season with salt and pepper to taste.

Fold in the cooked egg noodles or serve the sauce generously over the top. Garnish with plenty of fresh parsley.