Irish Beef Stew

In a large Dutch oven over medium heat, heat 2 tablespoons oil. Season beef with salt and pepper, then add to pot and cook on all sides until seared, 10 minutes, working in batches if necessary. Transfer beef to a plate.  In same pot, add remaining tablespoon oil and cook onion, carrots, and celery until soft, 5 minutes. Season with salt and pepper. Add garlic and cook until fragrant, 1 minute. Add beef back to Dutch oven, then add potatoes, broth, beer, and thyme. Bring to a boil, then reduce heat to a simmer. Season with salt and pepper. Cover and let simmer until beef and potatoes are tender, 30 minutes. Garnish with parsley before serving.