If you are using fresh lemon grass, discard the outer leaves and upper half of the stalk. Slice paper-thin; chop very fine. If you are using dried lemon grass, soak in warm water for 1 hour. Drain and finely chop.
In a bowl, combine the beef with the lemon grass, chiles, sugar, ginger, cinnamon, curry powder, fish sauce and black pepper to taste. Sprinkle in 1 teaspoon of the salt; mix well. Let stand for 30 minutes.
Heat 2 tablespoons of the oil in a large, heavy saucepan or pot over high heat. Add the beef and marinade and stir quickly to sear, about 2 minutes. Remove the meat to a bowl.
Add the remaining 1 tablespoon oil to the saucepan. When the oil is hot, add the onion and garlic and stir-fry until fragrant, about 1 minute. Add the tomato paste and stir for 2 minutes. Add the beef, star anise, the remaining 1 teaspoon salt and 4 cups of water. Bring the mixture to a boil. Reduce the heat to low, cover the pan and simmer until the beef is tender, about 1 1/2 hours.
Add the carrots and simmer for 10 minutes. Add the potatoes and continue simmering for 10 minutes longer. Add the daikon and cook for another 10 minutes.