Heat olive oil in a large pot or Dutch oven over medium-high heat.
- Season beef cubes with salt and pepper, then brown in batches. Remove and set aside.
- In the same pot, sauté onions, garlic, carrots, and celery until softened.
- Stir in tomato paste and cook for 1–2 minutes to develop flavor.
- Return beef to the pot and add beef broth, Worcestershire sauce, bay leaves, and thyme. Bring to a boil.
- Reduce heat to low, cover, and simmer for 1½–2 hours, or until beef is tender.
- Add sweet potatoes and cook for 20–25 minutes, until tender but not mushy.
- For a thicker stew, whisk cornstarch with water and stir in during the last 5 minutes of cooking.
- Remove bay leaves, garnish with parsley, and serve hot.