Heat the olive oil in a large deep pot or Dutch oven over medium-high heat. Add the ground beef and 1/4 teaspoon of the salt. Cook for 5 to 6 minutes, breaking it into crumbles, until well browned and the ground beef reaches 160°F on a food thermometer. Drain excess fat and transfer the beef to a plate.

Return the pot to medium heat and melt the butter. Add the onion, mushrooms and 1/4 teaspoon of the salt. Cook for 5 to 6 minutes, stirring occasionally, until the onion softens and the mushrooms are golden and have released their liquid. Add the garlic and cook for 1 minute.

Sprinkle the flour over the vegetables. Stir constantly for 1 minute, then gradually pour in the beef broth, stirring to prevent lumps. Add 1 tablespoon of the Worcestershire sauce, the Dijon mustard, the remaining 1/2 teaspoon salt and the black pepper. Return the beef to the pot.

Stir in the dry egg noodles so they are submerged. Bring to a boil, then reduce to a steady simmer. Cover and cook for 8 to 10 minutes, stirring every couple of minutes, until the noodles are tender and have absorbed most of the liquid.

Remove the pot from the heat and let it stand for 2 minutes. Stir in the remaining 1 tablespoon Worcestershire sauce and the sour cream until smooth. Stir in the parsley, taste and adjust the seasoning before serving.