1. For the stock, place all ingredients except fish sauce in a saucepan over high heat until it comes to a boil, reduce heat and simmer for 20-30 minutes. Season with fish sauce OR soy sauce and teaspoon of VEGEMITE of your choice and strain, discarding solids, set aside.
2. Using a sharp knife, finely slice the beef fillet and separate into four portions. (Skip this step if using tofu).
3. Cook rice noodles in boiling water for 5-6 minutes, once cooked strain and transfer directly to bowls followed by the finely sliced beef OR tofu and reheated broth. The hot broth should cook the beef if being used.
4. Garnish with sliced spring onion, chili, Thai basil, bean sprouts and lime.