Prep the Beef: Start by patting your beef chunks dry, then season them generously with salt and pepper. Get your oven ready by preheating it to 325°F (160°C).
Brown the Beef: Heat 1 tablespoon of oil in a large Dutch oven over medium heat until hot. Add about half of the beef and cook, stirring occasionally, until all sides are beautifully browned. Remove this batch to a bowl and repeat with another tablespoon of oil and the rest of the beef.
Sauté Aromatics: Add the last tablespoon of oil to the same pan. Toss in the diced onion and chopped celery, cooking for about 4 minutes until they start to soften. Stir in the fresh rosemary or thyme, tomato paste, and minced garlic, cooking for just 1 more minute until everything smells wonderful.
Build the Broth: Pour in the red wine and let it simmer for about 2 minutes until it has reduced by half. Next, stir in the beef broth and bring the mixture to a gentle simmer. Return all the browned beef and any accumulated juices from the bowl back into the pot.
Slow Simmer (First Round): Cover your Dutch oven tightly with its lid. Carefully transfer it to the preheated oven and let it cook for 1 hour, allowing the beef to become tender.
Add Veggies & Continue Simmering: Take the pot out of the oven. Stir in the chopped zucchini, cubed turnip, and optional carrots. Give everything a good stir to combine. Put the lid back on and return it to the oven for another 30 to 45 minutes, or until all the vegetables are perfectly tender.
Thicken & Serve: To thicken your delicious stew, gently push the meat and vegetables to one side of the pot. Whisk the glucomannan (or xanthan gum) into the liquid until it's well combined. The stew will continue to thicken as it rests. Serve warm and enjoy!