Season the beef with salt and pepper and toss lightly with the flour. Heat the butter and olive oil in a large Dutch oven over medium-high heat. Sear the beef in two batches until lightly browned on all sides (it will not be cooked through). Remove and set aside.
Add the onions and celery to the pot with a sprinkle of salt. Saute about 5 minutes, until softened.
Stir in the rosemary, anchovies, and garlic. Add the tomato paste and cook 1 minute, stirring.
Pour in the balsamic vinegar, scraping up the browned bits from the bottom of the pot. Stir in the soy sauce.
Return the beef and any juices to the pot. Add the broth and the thyme bundle. Bring to a gentle simmer, partially cover, and cook 1 1/2 to 2 hours, until the beef begins to get tender.
Stir in the pumpkin puree. Add the carrots, honey nut squash, potatoes, and 1 teaspoon salt. Cover and simmer about 30 minutes, until the vegetables are tender and the beef is fork tender.
Uncover and simmer until the broth reduces to a rich, gravy-like consistency, about 15 more minutes. Taste and adjust the salt, then add a small splash of balsamic vinegar at the end to brighten the flavor.
Ladle into bowls and serve with buttered sourdough toast.