Dredge the Beef: Place the beef chunks and flour in a large bowl. Toss until every side of the meat is evenly coated in a thin layer of flour.
Sear for Flavor: In a large, heavy-bottomed soup pot or Dutch oven, melt the butter over medium-high heat. Working in small batches, brown the beef on all sides. Do not overcrowd the pan, or the meat will steam rather than sear. Remove each batch and set aside in a bowl.
Aromatics: Once all meat is removed, add the onion and garlic to the pot. Sauté for 1–2 minutes, using a wooden spoon to scrape up all the flavorful browned bits from the bottom.
The Long Simmer: Return the beef to the pot. Add the beef stock, pumpkin puree, Worcestershire sauce, salt, and pepper. Stir thoroughly and bring to a boil.
Low and Slow: Reduce the heat to medium-low, cover, and let it simmer for 3 hours. Stir occasionally to ensure the pumpkin doesn't stick to the bottom.
Add the Root Veggies: Stir in the potatoes, carrots, and thyme sprigs. Increase the heat to medium and cook for an additional 30–40 minutes until the vegetables are tender.
Final Seasoning: Remove the thyme stems. Taste the broth and add additional salt if needed. Serve hot in deep bowls.