LOAD CROCK POT: Add 1 1/2 pounds chuck roast, trimmed and cut into 1 to 1 ½-inch cubes to a 6-quart slow cooker. Sprinkle with 1 teaspoon kosher salt and 1/2 teaspoon fresh ground black pepper.
ADD LIQUID AND VEGETABLES: Pour in 1 1/4 cups beef stock. Add 6 ounces coarsely chopped white mushrooms, 1 medium yellow onion, chopped , 3 tablespoons Worcestershire sauce, 1 tablespoon Dijon mustard, heaping , 2 cloves garlic, minced, 1 teaspoon dried parsley, and 1/2 teaspoon dried thyme. Stir gently to combine.
COOK: Cover and cook on LOW for 8 to 9 hours or HIGH for 4 to 5 hours, until the beef is fork-tender and easily shreds.
COOK NOODLES: About 20 minutes before serving, cook 12 ounces egg noodles according to package directions. Drain well.
FINISH: Stir the cooked noodles and 1 cup sour cream into the slow cooker. Cook on LOW for another 10 to 15 minutes, stirring occasionally, until creamy and heated through.
SERVE: Serve hot.
Notes
Low and Slow: Cooking on LOW yields the most tender beef.Make-Ahead: The beef mixture can be cooked a day ahead. Reheat gently, then stir in freshly cooked noodles and sour cream before serving.Storage: Store leftovers in an airtight container in the refrigerator for up to 3 days.Freezing: Freeze the beef mixture without noodles for up to 2 months. Thaw overnight in the refrigerator and reheat before adding freshly cooked noodles.Pro Tip: If the sauce seems thin before adding noodles, remove the lid for the last 30 minutes of cook time to reduce slightly.