2 tablespoons butter
12 ounces mushrooms, thickly sliced
1/2 medium sweet onion, diced
Kosher salt and freshly ground black pepper, to taste
1 pound lean ground beef
2 cloves garlic, minced
1/2 teaspoon dried thyme
3 tablespoons all-purpose flour
1/4 cup dry white wine
4 cups beef stock
2 tablespoons Worcestershire sauce
1 tablespoon Dijon mustard
8 ounces egg noodles, uncooked
1/2 cup sour cream
Melt butter in a large skillet over medium heat. Add mushrooms and onion, and cook, stirring occasionally, until mushrooms are tender and browned, about 3-5 minutes; season with salt and pepper, to taste.
Add ground beef and cook until browned, about 3-5 minutes, making sure to crumble the beef as it cooks. Stir in garlic and thyme until fragrant, about 1 minute.
Whisk in flour until lightly browned, about 1 minute.
Stir in wine, scraping any browned bits from the bottom of the skillet.
Stir in beef stock, Worcestershire, Dijon and egg noodles; season with salt and pepper, to taste. Bring to a boil; cover, reduce heat and simmer until pasta is cooked through, about 9-10 minutes.
Stir in sour cream until heated through, about 1-2 minutes.