Start by seasoning the beef chunks with salt and pepper, then heat vegetable oil in a skillet until shimmering. Brown the beef in batches over medium-high heat until each side develops a deep, golden crust—this helps build rich flavor.
Once browned, transfer the beef to your slow cooker and add the sliced carrots, chopped parsnips, and diced potatoes. Spread the vegetables evenly around the meat for balanced cooking.
In the same skillet, add a bit more oil if needed and sauté the minced garlic until fragrant, about 30 seconds, and then stir in the tomato paste. Cook briefly until the mixture darkens slightly—this releases full flavor and aroma.
Pour the garlic and tomato paste mixture over the beef and vegetables in the slow cooker. Add the fresh thyme leaves and pour in the beef broth, covering all ingredients with liquid.
Cover the slow cooker and set it to low. Let it cook undisturbed for about 4 hours, or until the beef is tender and the vegetables are soft and melting into the sauce.
Once cooked, open the lid and check the stew's consistency. If you prefer a thicker gravy, stir in a cornstarch slurry and cook on high for another 10 minutes until it reaches your desired thickness.
Taste and adjust the seasoning with more salt and pepper as needed. Serve the stew hot, garnished with fresh herbs if desired, and enjoy the hearty, flavorful dish.