Prep & Sear the Beef: Pat your beef chunks dry and season them generously with salt and pepper. Preheat your oven to a cozy 325°F. In a large Dutch oven over medium heat, add 1 tablespoon of oil. Brown about half of the beef until it's nicely golden on all sides, then transfer it to a bowl. Repeat this with another tablespoon of oil and the remaining beef.
Sauté the Aromatics: Add the last tablespoon of oil to the pot. Toss in the diced onion and chopped celery, sautéing 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.
Deglaze & Simmer: Pour in the red wine (if using) and let it bubble gently, cooking until it reduces by about half (roughly 2 minutes). Stir in the beef broth and bring the mixture to a light simmer.
Oven Time: Return all the browned beef and any yummy juices from the bowl back into the Dutch oven. Give it a good stir, then cover the pot with a tight-fitting lid. Carefully transfer it to your preheated oven and let it cook for 1 hour.
Add Veggies & Finish: Take the pot out of the oven. Stir in the chopped zucchini, cubed turnip, and the optional carrots. Return the covered pot to the oven and continue to cook for another 30 to 45 minutes, or until all the vegetables are perfectly tender and the beef is melt-in-your-mouth soft.
Thicken (Optional): If you like your stew broth a little thicker, gently push the meat and vegetables to one side. Sprinkle the glucomannan into the simmering liquid, whisking continuously until it slightly thickens. It will continue to thicken as it sits.
Serve & Enjoy: Ladle out this hearty, warming stew and savor every delicious, healthy bite!