Prepare the chuck roast by letting it sit at room temperature for 15 minutes. Chop the butternut squash, turnip, and carrots into uniform pieces.

In a Dutch oven, heat olive oil and butter until shimmering. Brown the beef in batches for about 4 minutes on each side, then set aside.

Sauté the shallots in the same pot for 3 minutes, then add minced garlic and cook for an additional minute. Stir in tomato paste and Dijon mustard.

Pour in red wine to deglaze the pot, reducing it by half. Return the beef, add thyme, rosemary, Worcestershire sauce, and beef stock. Bring to a boil.

Cover and simmer for 1 hour and 15 minutes until the beef is tender.

Add the diced butternut squash, turnip, and carrots. Simmer for an additional 45 minutes.

Mix cornstarch with beef stock. Bring stew to a gentle boil and stir in the cornstarch mixture, cooking for another 2 minutes until thickened.

Remove thyme and rosemary sprigs, adjust seasoning, and serve hot, ideally with bread.