Heat 1 tablespoon of olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat. Add the ground beef and cook, breaking it up with a spoon, until fully browned and no pink remains. Drain any excess fat and set the beef aside.

In the same pot, add the remaining 1 tablespoon of olive oil. Add the sliced onions and cook over medium heat for 8-10 minutes, stirring occasionally, until softened and lightly caramelized.

Add the sliced mushrooms to the pot and cook for another 5-7 minutes, until they release their liquid and start to brown. Stir in the minced garlic, diced carrots, and diced celery, cooking for 3-4 minutes until slightly softened and fragrant.

Sprinkle the all-purpose flour over the vegetables in the pot and cook, stirring constantly, for 1-2 minutes to create a roux. This will help thicken the soup.

Gradually whisk in the beef broth, ensuring there are no lumps. Stir in the Worcestershire sauce, dried thyme, and crushed dried rosemary. Bring the mixture to a simmer, scraping up any browned bits from the bottom of the pot.

Return the cooked ground beef to the pot. Reduce the heat to low, cover, and let the soup simmer for at least 25-30 minutes, or until the vegetables are tender and the flavors have melded. Stir occasionally.

If desired, stir in the heavy cream during the last 5 minutes of cooking for a richer, creamier soup. Season the soup generously with salt and freshly ground black pepper to taste.

Ladle the hot soup into bowls. Garnish with fresh chopped parsley before serving. This soup pairs wonderfully with crusty bread or a side salad.