Pat beef dry and season generously with salt and pepper.
Heat olive oil in a large Dutch oven over medium-high heat and brown beef in batches (do not crowd), then transfer to a plate.
Reduce heat to medium, add onion and cook until soft (5 min), then stir in garlic and tomato paste and cook for 1 minute.
Pour in red wine, scraping up browned bits from the bottom, and let it simmer for 5 minutes until reduced by half.
Return beef to the pot, add beef broth, thyme, and bay leaves, bring to a boil, then reduce to a low simmer.
Cover and cook for 1.5 hours, then add carrots, parsnips, and potatoes and continue simmering for 45 more minutes until vegetables are tender and meat is fork-tender.
(Optional) For thicker stew, whisk flour with 3 tbsp water and stir in; cook 10 more minutes.
Remove thyme stems and bay leaves, adjust salt and pepper to taste, and serve hot.
