Preheat the oven to 400°F (200°C).

In a large skillet, brown the ground beef over medium heat. Drain excess fat.

Add the onion and garlic to the skillet and sauté until softened, about 3-5 minutes.

Stir in the carrots and celery, and cook for another 5 minutes, allowing the vegetables to soften.

Add the diced tomatoes, beef broth, Worcestershire sauce, dried thyme, salt, and pepper. Bring the mixture to a simmer.

In a bowl, combine the flour, baking powder, and salt. Stir in the milk and melted butter until just combined; do not overmix.

Drop spoonfuls of the dumpling batter over the simmering beef mixture, covering as much of the surface as possible.

Transfer the skillet or mixture to a preheated oven and bake for 20-25 minutes, or until the dumplings have risen and are golden brown.

Remove from the oven and let it cool for a few minutes. Garnish with fresh parsley if desired before serving.