Heat olive oil in a large pot over medium heat.
Add onion, carrots, and celery. Sauté for 5 minutes until softened.
Stir in garlic and cook for 30 seconds until fragrant.
Pour in broth, add thyme, bay leaf, salt, and pepper. Bring to a simmer.
In a mixing bowl, whisk flour, baking powder, and salt.
Add milk, melted butter, and parsley. Stir until just combined (do not overmix).
Drop spoonfuls of dumpling dough (about 1 tbsp each) into the simmering soup.
Cover and cook for 15 minutes (do not lift the lid).
Remove the bay leaf.
Ladle soup into bowls, ensuring each serving has dumplings.
Garnish with fresh parsley if desired.
