Place the sliced beef in a bowl with all the marinade ingredients. Mix well, cover, and refrigerate for at least 15 minutes.
Prepare all vegetables and set aside.
In a separate bowl, mix all the sauce ingredients until well combined. Set aside.
Place the dried egg noodles in a large heatproof bowl. Cover with boiling water and leave for 2 minutes. Drain through a sieve and spread on a tray lined with kitchen paper to dry slightly.
Heat a 24 cm frying pan with enough oil to coat the base. Spread the noodles evenly to form a thin pancake.
Fry over medium heat for 3 to 4 minutes on each side until golden and crispy. Transfer to a plate and set aside.
Heat a wok over medium-high heat with a little oil. Add garlic and red onion and stir-fry for 20 seconds until fragrant.
Add the marinated beef and stir-fry for about 3 minutes until just cooked.
Add red and green peppers and stir-fry for a further 3 to 4 minutes.
Add spring onions and the prepared sauce. Stir-fry for 2 to 3 minutes until the sauce thickens and coats the beef.
Spoon the beef stir-fry over the centre of the crispy noodle pancake. Serve immediately.