Preheat oven to 250°. Heat 3 tbsp of oil over medium heat. Add the carrots, garlic, and thyme, and cook until lightly browned. Season with the salt and pinch of nutmeg, transfer to a dish and keep warm.
Add the beef to the pan and cook until browned on all sides. Season with salt, add the brandy and cook until it is evaporated. Transfer the beef to a roasting pan, place the carrots around the roast and sprinkle with the celery leaves. Drizzle the remaining 2 tbsp of olive oil over the roast and carrots and bake for 2 hours or until carrots are caramelized. If the carrots get caramelized before the roast is tender, remove the carrots and continue cooking until the beef is tender, then add the carrots back and heat through. (This could take up to 30 to 45 minutes depending on the thickness of your roast.)
Remove the meat from the roasting pan, carve into slices and season with pepper. Transfer to a serving dish surrounded by carrots.