Heat a wide pot over medium heat. Once it is hot add the oil.
Saute the onion, carrots, celery, and garlic until the celery starts to soften. Crumbled in the beef and brown well while breaking it up into smaller pieces. Season with salt and pepper.
Stir in the broth, kitchen bouquet, and thyme. Cover with a lid and bring to a simmer for about 20 minutes to build flavor. Stir in the peas.
For the dumplings: In a large bowl, whisk together flour, baking powder, pepper, and salt. Make a well in the center of the flour mixture and mix in the milk a little at a time until a very thick batter forms. (Thicker than pancake batter should be the consistency)
Using a teaspoon, scoop the batter in mounds directly into the simmering soup. Space the mounds around the pot so they do not stick together. Let cook for 2 to 3 minutes then gently flip over and cook for 2 to 3 minutes longer until dumplings are firm.
Taste and adjust the seasoning with salt and pepper if needed. Add the cornstarch to thicken if needed. Remove the thyme sprigs before serving. Serve with a hunk of bread.