Soak the noodles: Put the rice noodles in warm water for about 10 minutes until flexible and pliable but not overly soft. Drain and set aside.
Make the sauce: Combine the caster sugar, fish sauce, tamarind paste and chilli sauce in a small bowl and stir well.
Stir-fry the aromatics: Heat the oil in a wok until hot. Add the shallot, garlic and chilli and stir over a medium heat until fragrant.
Sear the beef: Tip in the beef and stir-fry for one minute so it is still rare. Remove to a plate with a slotted spoon and set aside.
Cook the noodles: Add the drained noodles to the wok with the sauce and a splash of water. Stir-fry for a few minutes until tender.
Scramble the eggs: Push the noodles to one side, add a little more oil and crack the eggs over it. Scramble lightly until almost cooked, then fold into the noodles.
Finish the dish: Return the beef to the wok and add the beansprouts, spring onions, lime juice, palm sugar and both soy sauces. Stir briefly until the vegetables are slightly wilted but still crunchy.
Serve: Divide among warm shallow bowls, sprinkle with peanuts and serve immediately with lime wedges.
