In a large bowl, toss the beef cubes with ¼ cup of flour until evenly coated.
Place the floured beef, chopped onion, sliced carrots, and sliced celery in the slow cooker.
In a separate bowl, whisk together the beef broth, tomato paste, Worcestershire sauce, garlic, dried thyme, salt, and pepper. Pour this mixture over the beef and vegetables in the slow cooker.
Cover and cook on low for 8 hours. If desired, add a cornstarch slurry to thicken the stew (see notes*) just before adding the dumplings.
Around the 7-hour mark, start preparing the dumplings: In a medium bowl, mix together 1 ½ cups flour, baking powder, Italian seasoning, and ½ teaspoon salt. Stir in the melted butter and milk until a soft dough forms.
Drop large spoon-full dollops of the dumpling dough on top of the stew.
Cover and cook on high for an additional 50 minutes to 1 hour, or until the dumplings are cooked through.
Ladle into bowls, garnish with chopped fresh parsley (if desired), and serve hot.
Video
Notes
*For extra thickening: Use a slurry of 2 tablespoons cornstarch and 2 tablespoons of cold water to thicken up the stew. Add the cornstarch slurry right before adding the dumplings for a thick consistency.Storage: Leftovers should be stored in an airtight container in the refrigerator, where it will keep for up to 3-4 days.To Reheat: Reheat in the microwave in a pot or saucepan and warm it over medium heat for about 10-15 minutes, stirring occasionally. Add a little water or broth if needed to adjust the consistency.To freeze: It's best to freeze the stew without the dumplings, as they may become soggy upon thawing. Store the stew without the dumplings in a freezer-safe container or a plastic freezer bag for up to 2-3 months. Thaw it in the refrigerator overnight before reheating. When you're ready to serve it again, you can prepare a fresh batch of dumplings to add to the stew.